Powertrain control device

Abstract

To achieve high-level emission performance without impairing driving performance.SOLUTION: A powertrain control device 10 is for a vehicle that is provided with an exhaust emission control device 52 and an automatic transmission 3, and that travels while controlling an engine 2 and the automatic transmission 3. The powertrain control device has: an ECM (Engine Control Module) 11 that executes full-range theoretical air-fuel ratio operation control, and that, when an intake air charge amount reaches an upper limit value, which is set so that the temperature of a three-way catalyst does not exceed an allowable temperature, executes intake air charge amount limiting control; and a TCM (Transmission Control Module) 12 executes automatic shift control, and that, when an engine rotation speed reaches a rev limit, executes forced upshift control to forcibly upshift the automatic transmission 3. When the ECM 11 limits the intake air charge amount, the TCM 12 executes rev limit change control to lower the rev limit.SELECTED DRAWING: Figure 5B

Description

[Technical Field]

[0001] The disclosed technology relates to a powertrain control device for a vehicle equipped with an engine that operates at a stoichiometric air-fuel ratio throughout the entire operating range. [Background technology]

[0002] In recent years, regulations on exhaust emissions have been getting stricter from the perspective of environmental protection. Vehicles that run on engines (so-called engine vehicles) are the main targets of emissions regulations because they emit exhaust gases.

[0003] For this reason, efforts have been made to improve emissions performance in gasoline-fueled vehicles. In the case of gasoline-fueled engine vehicles, three-way catalysts can effectively remove the main exhaust emissions (hydrocarbons, carbon monoxide, and nitrogen oxides).

[0004] Therefore, three-way catalysts are one of the most effective means for such engine vehicles. Currently, exhaust gas purification devices using three-way catalysts are widely used.

[0005] The purification rate of exhaust gas by a three-way catalyst is affected by the air-fuel ratio (A / F). In other words, to achieve a high purification rate, it is necessary to stabilize the air-fuel ratio at the stoichiometric air-fuel ratio (14.7) or within a narrow range around it (the so-called window). Therefore, in order to achieve advanced emissions performance such as zero emissions in an internal combustion engine vehicle, it is necessary to operate within the window throughout the entire operating range of the engine (herein referred to as "full-range stoichiometric air-fuel ratio operation").

[0006] On the other hand, if a three-way catalyst is exposed to excessively high temperatures for a long period of time, its durability will decrease due to thermal degradation. Therefore, exhaust gas purification devices using a three-way catalyst must be temperature-controlled so as not to exceed its allowable temperature. In contrast, when operating at a full stoichiometric air-fuel ratio, combustion becomes more efficient and the heat value of the exhaust gas increases. As a result, in the operating range where the heat value of the exhaust gas is greatest, i.e., in the range of high engine speed and load, the temperature of the three-way catalyst may exceed the allowable temperature.

[0007] Generally, in operating ranges where the temperature of the three-way catalyst is likely to exceed the allowable temperature, a technology that increases the amount of fuel (so-called enriched control) is used. This technology uses the heat of vaporization of the fuel to reduce the heat content of the exhaust gas, thereby suppressing thermal degradation of the three-way catalyst. However, because the stoichiometric air-fuel ratio is not achieved, exhaust emissions cannot be effectively removed. Therefore, advanced emissions performance cannot be achieved.

[0008] In response to this, a technology has been proposed that prevents the temperature of the three-way catalyst from exceeding a permissible temperature even when operating at a stoichiometric air-fuel ratio across the entire engine range (Patent Document 1). In this technology, a second throttle valve is provided in addition to the original throttle valve. The second throttle valve is then adjusted to restrict the upper limit of the throttle opening so that the temperature of the three-way catalyst does not exceed the permissible temperature. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 8-158896 Summary of the Invention [Problem to be solved by the invention]

[0010] By applying the technology of Patent Document 1, it is possible to prevent the temperature of the three-way catalyst from exceeding the allowable temperature even when operating at the stoichiometric air-fuel ratio across the entire range.

[0011] However, the technology in Patent Document 1 restricts the throttle opening. This causes the intake air charge amount to be less than the required amount, resulting in insufficient engine output. As a result, the vehicle speed may not increase even when the accelerator pedal is depressed. In an automatic transmission, if the vehicle speed does not increase, the gears will not be shifted up. This makes it impossible for the vehicle to travel in accordance with the driver's operation, resulting in a decrease in vehicle driving performance.

[0012] Therefore, this specification discloses a technology that enables operation at the stoichiometric air-fuel ratio over the entire range while maintaining the three-way catalyst at an appropriate temperature, and also suppresses a decrease in the driving performance of the vehicle. [Means for solving the problem]

[0013] The disclosed technology relates to a powertrain control device for a vehicle that is equipped with an engine that runs by burning gasoline, an exhaust gas purification device that purifies exhaust gas emitted from the engine using a three-way catalyst, and an automatic transmission that automatically changes the output of the engine, and that drives the vehicle by controlling the engine and the automatic transmission.

[0014] The powertrain control device includes an engine control unit and a transmission control unit.

[0015] The engine control unit executes full-range stoichiometric air-fuel ratio operation control to control the operation of the engine so that the stoichiometric air-fuel ratio is maintained throughout the entire operating range, and also executes intake air charge amount limiting control to limit the intake air charge amount when the intake air charge amount reaches an upper limit value set so that the temperature of the three-way catalyst does not exceed an allowable temperature.

[0016] The transmission control unit executes automatic shift control to control the operation of the automatic transmission based on a shift map set based on an accelerator opening and a vehicle speed, and also executes forced upshift control to forcibly upshift the automatic transmission when the engine speed reaches a rev limit set to prevent the engine speed from exceeding an allowable limit.

[0017] When the engine control unit limits the intake air filling amount, the transmission control unit executes rev limit change control to lower the rev limit.

[0018] That is, according to this powertrain control device, since operation control is performed at the stoichiometric air-fuel ratio over the entire engine range, the purification rate of the exhaust gas purification device can be kept high at all times, thereby achieving high-level emission performance.

[0019] Furthermore, because intake air charge limiting control is executed, thermal degradation of the three-way catalyst can be suppressed even when full-range stoichiometric air-fuel ratio operation control is executed. However, as described above, when the intake air charge limiting control restricts the intake air charge, engine output becomes insufficient. As a result, the vehicle speed may not increase even when the accelerator pedal is depressed. Since the vehicle cannot travel in accordance with the driver's operation, the vehicle's driving performance deteriorates.

[0020] In response to this, this powertrain control device is configured to execute forced upshift control, which forcibly upshifts the automatic transmission when the engine speed reaches the rev limit in order to prevent the engine from over-revving. Therefore, by utilizing this forced upshift control, the powertrain control device is devised to obtain engine power and increase vehicle speed even when the intake air filling amount limiting control is executed.

[0021] That is, when the engine control unit limits the intake air charge, the transmission control unit executes rev limit change control to lower the rev limit. By lowering the rev limit, the rev limit is reached at a normal engine speed that is lower than the overspeed limit. When the engine speed reaches the rev limit, the automatic transmission is forced to upshift through forced upshift control.

[0022] As a result, the gear ratio of the automatic transmission decreases and the engine speed decreases while maintaining the vehicle speed. As the engine speed decreases, the intake air charge limit is relaxed accordingly, allowing the engine to obtain power. As the engine speed and vehicle speed increase, the deterioration of vehicle driving performance is also suppressed.

[0023] The amount of reduction of the rev limit in the rev limit change control may be set to differ depending on the gear position of the automatic transmission, with the amount of reduction being greater for a higher gear position than for a lower gear position.

[0024] This allows the vehicle speed to be increased more quickly in lower gears, further minimizing the deterioration of the vehicle's driving performance.

[0025] It is preferable that the upper limit of the intake air filling amount be set smaller as at least one of the engine speed, intake air temperature, and engine coolant temperature increases.

[0026] These state values ​​are highly correlated with the upper limit of the intake air charge amount. That is, the higher the engine speed, the greater the amount of exhaust heat from the engine and the higher the temperature of the three-way catalyst. Therefore, it is preferable to set the upper limit of the intake air charge amount lower, i.e., to make the restriction stricter, as the engine speed increases.

[0027] This allows a good balance between suppressing thermal deterioration of the three-way catalyst and suppressing a decrease in engine output. The same applies to the intake air temperature and the engine coolant temperature.

[0028] If it is determined that there is a high possibility that the temperature of the three-way catalyst will exceed the allowable temperature, an upper limit value of the intake air filling amount may be calculated based on three values ​​consisting of the engine speed, the intake air temperature, and the engine coolant temperature, and a predetermined reference state value.

[0029] In other words, in a high-risk state, there is a high possibility that the intake air charge amount will be limited. Restricting the intake air charge amount reduces engine output. Therefore, in order to prevent a reduction in engine output, it is preferable that the upper limit of the intake air charge amount be highly reliable.

[0030] Therefore, this powertrain control device detects three state values ​​that are highly correlated. Then, based on the detected values ​​and a predetermined reference state value, it calculates the upper limit of the intake air charge amount. By doing so, it is possible to obtain the upper limit of the intake air charge amount with high estimation accuracy, and it is possible to suppress a decrease in engine output.

[0031] If it is determined that the temperature of the three-way catalyst is unlikely to exceed the allowable temperature, an upper limit value of the intake air filling amount may be calculated based on two values ​​consisting of the engine speed and the intake air temperature and a predetermined reference state value.

[0032] The temperature of the three-way catalyst is particularly dependent on engine speed and intake air temperature. In a low-risk state, the intake air charge amount is unlikely to be limited. Therefore, this calculation method allows for a simple calculation of the necessary and sufficiently reliable upper limit of the intake air charge amount. This is efficient and reduces the computational burden of control.

[0033] If the engine has a swirl control valve that changes the strength of the swirl flow generated in the combustion chamber by adjusting the opening, the upper limit value of the intake air filling amount may be corrected based on the deviation of the opening of the swirl control valve from the reference state value.

[0034] The deviation in the opening degree of the swirl valve causes variations in the calculation of the upper limit of the intake air charge amount. Therefore, if the upper limit of the intake air charge amount is corrected based on the deviation, the upper limit of the intake air charge amount can be estimated with even higher accuracy.

[0035] If the engine has a variable valve timing mechanism that enables adjustment of the opening and closing timing of the intake valve and / or the exhaust valve, the upper limit value of the intake air filling amount may be corrected based on the deviation of the opening and closing timing of the intake valve and / or the exhaust valve from the reference state value.

[0036] The difference in opening and closing timing causes variations in the calculation of the upper limit of the intake air charge amount. Therefore, if the upper limit of the intake air charge amount is corrected based on the amount of this difference, the upper limit of the intake air charge amount can be estimated with even greater accuracy.

[0037] If the engine has an EGR valve that changes the amount of recirculated exhaust gas by adjusting its opening, the upper limit value of the intake air filling amount may be corrected based on the deviation of the opening of the EGR valve from the reference state value.

[0038] The deviation in the EGR valve opening causes variations in the calculation of the upper limit of the intake air charge amount. Therefore, if the upper limit of the intake air charge amount is corrected based on the deviation, the upper limit of the intake air charge amount can be estimated with even higher accuracy.

[0039] When the engine control unit further performs ignition retard control to retard the ignition timing in order to suppress knocking, the upper limit value of the intake air filling amount may be corrected based on the amount of retardation of the ignition timing relative to the reference state value.

[0040] The retard amount can cause variations in the calculation of the upper limit of the intake air charge amount. Therefore, if the upper limit of the intake air charge amount is corrected based on the retard amount, the upper limit of the intake air charge amount can be estimated with even higher accuracy.

[0041] When the transmission control unit executes the rev limit change control, if the acceleration of the vehicle is equal to or less than a preset acceleration feeling discrimination boundary value, the transmission control unit may execute early forced upshift control to forcibly upshift the automatic transmission when the vehicle reaches a predetermined engine speed lower than a temporary rev limit set by the rev limit change control. Note that the "acceleration feeling discrimination boundary value" here refers to a boundary value of an acceleration range at which the driver can discern the feeling of acceleration.

[0042] When the above-described control is performed, the power of the engine itself is limited when the vehicle is accelerated under conditions where the engine is running at high speed and under high load, which can result in the engine noise being perceived as noisy during acceleration.

[0043] On the other hand, if such early forced upshift control is executed, the engine speed decreases at an earlier timing. As a result, the engine noise becomes quieter, and the engine noise can be suppressed. If the vehicle acceleration is higher than the acceleration sensation discrimination threshold, the driver can feel the acceleration sensation, but if it falls below that threshold, the driver will not feel the acceleration sensation. On the other hand, if early forced upshift control is executed, the gear ratio changes, and the sluggish sensation can be eliminated. Therefore, the acceleration sensation can be ensured.

[0044] The early forced upshift control may be executed only when the acceleration of the vehicle after the upshift is predicted to be equal to or greater than a preset threshold value for identifying a stall feeling.

[0045] This allows the acceleration of the vehicle to be stably maintained within a range that allows the driver to feel a sense of acceleration. Therefore, the driver does not feel a sluggish acceleration before the upshift, as long as the acceleration feeling after the upshift is maintained within the range.

[0046] The early forced upshift control may be executed only when the engine speed is a predetermined high speed in a specific gear position of the automatic transmission.

[0047] In other words, early forced upshift control is particularly effective at specific gear stages and at specific engine speeds where the driver feels a sense of sluggish acceleration due to the execution of forced upshift control, and can achieve excellent results. [Effects of the Invention]

[0048] A powertrain control device incorporating the disclosed technology can maintain the three-way catalyst at an appropriate temperature while maintaining stoichiometric air-fuel ratio operation across the entire engine range. Furthermore, it can also suppress a decrease in vehicle speed response due to insufficient engine output. This allows engine vehicles to achieve high-level emissions performance without sacrificing driving performance. [Brief explanation of the drawings]

[0049] [Figure 1] 1 is a diagram showing the main configuration of an automobile to which the disclosed technology is applied. [Figure 2] FIG. 1 is a diagram showing the main configuration of an engine. [Figure 3] 1 is a block diagram showing the relationship between a powertrain control device and its main associated devices; [Figure 4] 3 is an example of a shift map. [Figure 5A] FIG. 1 is a diagram for explaining a problem in intake air filling amount limiting control (prior art). [Figure 5B] FIG. 10 is a diagram for explaining an improvement in intake air filling amount limiting control (disclosed technology). [Figure 6] FIG. 10 is a diagram showing a specific example (table) of rev limits. [Figure 7] 10 is an example of a flowchart relating to full-range stoichiometric air-fuel ratio operation control. [Figure 8] 4 is an example of a flowchart relating to intake air filling amount limiting control. [Figure 9A] 10 is an example of a flowchart relating to forced upshift control and rev limit change control. [Figure 9B] 9B is a part of the flowchart of FIG. 9A. [Figure 10]FIG. 10 is an image diagram showing the relationship between main state values ​​and CE limit values. [Figure 11] FIG. 10 is a conceptual diagram showing the relationship between main state values ​​and correction values. [Figure 12] FIG. 10 is a diagram for explaining a problem that the modified example aims to solve. [Figure 13] 4 is a time chart relating to early forced upshift control. [Figure 14] FIG. 10 is a diagram showing a specific example (table) of rev limits in a modified example. [Figure 15] 10 is an example of a flowchart (part) of early forced upshift control. DETAILED DESCRIPTION OF THE INVENTION

[0050] The disclosed technology will be described below, but the following description is merely an example.

[0051] <Powertrain> Fig. 1 shows an automobile 1 (an example of a vehicle) to which the disclosed technology is applied. This automobile 1 is equipped with an engine 2 as a drive source (a so-called engine vehicle). The engine 2 is located in the front part (engine compartment) of the automobile 1. The automobile 1 travels by being driven by the engine 2.

[0052] (engine) The engine 2 is a reciprocating engine that burns gasoline in four strokes: intake, compression, expansion, and exhaust. In other words, the fuel for the engine 2 is gasoline. However, the fuel may be any fuel that is primarily gasoline, and may also contain components other than gasoline.

[0053] The engine 2 has four cylinders 20 arranged in series. Figure 2 shows the structure of the engine 2. Figure 2 shows one cylinder 20. A piston 22 connected to a crankshaft 21 is inserted into each cylinder 20 formed in the engine block 2a. A combustion chamber 23 is defined above the cylinder 20 by the piston 22.

[0054] The cylinder head 2b is provided with, for each cylinder 20, an injection valve 25, an ignition plug 26, a pair of intake valves 27, 27, a pair of exhaust valves 28, 28, an intake continuously variable valve timing mechanism (intake S-VT) 30, an exhaust continuously variable valve timing mechanism (exhaust S-VT) 31, a swirl control valve (SCV) 32, and the like.

[0055] The injection valve 25 is attached to the cylinder head 2b so that its injection port faces the combustion chamber 23. Gasoline is pressure-fed to the injection valve 25 by a fuel supply system (not shown). The injection valve 25 injects gasoline into the combustion chamber 23.

[0056] The spark plug 26 is attached to the cylinder head 2b so that its electrode faces the combustion chamber 23. The spark plug 26 ignites the air-fuel mixture formed in the combustion chamber 23.

[0057] As shown in the upper diagram of Figure 2 (viewed from above), a pair of intake ports 2c, 2c is provided in the cylinder head 2b. An intake valve 27 that opens and closes the passage of each intake port 2c, 2c is disposed in each of these intake ports 2c, 2c. The intake valve 27 opens and closes at predetermined timing by the drive of the intake S-VT 30.

[0058] The cylinder head 2b is also provided with a pair of exhaust ports 2d, 2d. Each of the exhaust ports 2d, 2d is provided with an exhaust valve 28 that opens and closes the passage. The exhaust valve 28 opens and closes at a predetermined timing by driving an exhaust S-VT 31.

[0059] A swirl control valve (SCV 32) is disposed upstream of one of the intake ports 2c, 2c. By adjusting the opening of the SCV 32, the strength of the circulating flow (swirl flow) in the combustion chamber 23 can be changed.

[0060] In other words, when the opening of the SCV 32 is large, there is almost no difference in the flow rate of intake air flowing into the combustion chamber 23 from each intake port 2c. Therefore, almost no swirl flow is generated. On the other hand, when the opening of the SCV 32 is small, there is a difference in the flow rate of intake air flowing into the combustion chamber 23 from the two intake ports 2c, 2c. This causes a swirl flow, as shown by arrow A1 in Figure 2. The smaller the opening of the SCV 32, the stronger the swirl flow.

[0061] The engine 2 (cylinder head 2b and engine block 2a) is provided with a cooling water passage 33 through which cooling water circulates. Low-temperature cooling water flows into the cooling water passage 33. After the cooling water is heated by heat exchange with the engine 2 and reaches a high temperature, it flows out of the cooling water passage 33. The engine 2 is cooled by the cooling water circulating through the engine 2.

[0062] As shown in Fig. 1, an intake passage 40 is connected to the engine 2. The intake passage 40 communicates with the intake ports 2c of each cylinder 20 via an intake manifold. A throttle valve 42 is disposed in the intake passage 40. The amount of air (amount of fresh air) supplied to the combustion chamber 23 is changed by adjusting the opening of the throttle valve 42.

[0063] An exhaust passage 50 is connected to the engine 2. The upstream side of the exhaust passage 50 communicates with the exhaust ports 2d of each cylinder 20. The downstream side of the exhaust passage 50 communicates with a muffler 51 disposed at the rear of the automobile 1. Exhaust gas generated in each combustion chamber 23 is discharged to the rear of the automobile 1 through the exhaust passage 50.

[0064] An exhaust gas purification device 52 is disposed in the exhaust passage 50. The exhaust gas purification device 52 includes a three-way catalyst. That is, the exhaust gas purification device 52 purifies the exhaust gas using the three-way catalyst.

[0065] An EGR passage 55 for recirculating exhaust gas is connected between the intake passage 40 and the exhaust passage 50. The EGR passage 55 returns a portion of the exhaust gas to the intake passage 40. An EGR valve 56 is disposed in the EGR passage 55. The amount of exhaust gas to be recirculated is changed by adjusting the opening of the EGR valve 56, thereby changing the EGR rate.

[0066] (automatic transmission) The automobile 1 is also equipped with a multi-speed automatic transmission 3 (so-called AT). The automatic transmission 3 automatically changes the output of the engine 2.

[0067] An input shaft 60 of the automatic transmission 3 is connected to the crankshaft 21 of the engine 2. An output shaft 61 of the automatic transmission 3 is connected to a differential gear 6 via a propeller shaft 5. A torque converter 62 and a transmission mechanism 63 are incorporated between the input shaft 60 and the output shaft 61.

[0068] The transmission mechanism 63 is made up of a plurality of planetary gear mechanisms 63a, a plurality of clutches 63b (including brakes), etc. By switching the transmission mechanism 63, it is possible to switch between forward and reverse, and to change to a different gear ratio between the input shaft 60 and the output shaft 61 of the automatic transmission 3, that is, to switch gear positions.

[0069] For example, the input side of each clutch 63b is configured to be connectable to the input shaft 60 via a torque converter 62. The output side of each clutch 63b is connected to the output shaft 61 via a corresponding planetary gear mechanism 63a.

[0070] When a specific clutch 63b is selected and engaged, the input shaft 60 and the output shaft 61 are connected via the clutch 63b and the corresponding planetary gear mechanism 63a, thereby changing the gear position.

[0071] As will be described later, the automatic transmission 3 is provided with 1st to 6th gears. The output of the engine 2 is changed in speed by the automatic transmission 3 and then transmitted to a differential gear 6 via a propeller shaft 5.

[0072] The differential gear 6 is connected to left and right drive wheels 8 via a pair of axles 7, 7. The output of the engine 2 is distributed to each axle 7 by the differential gear 6 and transmitted to each drive wheel 8. This allows the automobile 1 to travel.

[0073] <Powertrain control device> The automobile 1 is also equipped with a device (powertrain control device 10) that controls the above-mentioned powertrain. The powertrain control device 10 is composed of an engine control module (ECM) 11, a transmission control module (TCM) 12, a vehicle control module (VCM) 13, etc.

[0074] The ECM 11 corresponds to the "engine control unit." The TCM 12 corresponds to the "transmission control unit." The VCM 13 is a higher-level module than the ECM 11 and TCM 12. The VCM 13 controls the ECM 11 and TCM 12 comprehensively.

[0075] The ECM 11, TCM 12, and VCM 13 each include hardware such as a processor, memory, and interface, and software such as a database and control programs. These modules are connected by, for example, a Controller Area Network (CAN) and are configured to be able to electrically communicate with each other.

[0076] The configuration of the powertrain control device 10 can be changed according to the specifications. For example, the powertrain control device 10 may be configured with one module or with more modules.

[0077] <Various sensors> 1 and 2, various sensors are attached to the powertrain. Specifically, an accelerator opening sensor 70, a vehicle speed sensor 71, an engine speed sensor 72, a crank angle sensor 73, an airflow sensor 75, a coolant temperature sensor 76, an intake air temperature sensor 77, an exhaust temperature sensor 78, an SCV opening sensor 80, an EGR valve opening sensor 81, and a catalyst temperature sensor 82 are attached to the powertrain.

[0078] The powertrain control device 10 cooperates with these sensors to control the engine 2 and the automatic transmission 3. Figure 3 shows a block diagram showing the relationship between these various sensors, the powertrain control device 10, the engine 2, and the automatic transmission 3.

[0079] The accelerator opening sensor 70 is attached to the accelerator pedal. The accelerator opening sensor 70 detects the accelerator opening corresponding to the operation of the accelerator pedal. The vehicle speed sensor 71 is attached to a wheel hub or the like. The vehicle speed sensor 71 detects the speed of the automobile 1.

[0080] The engine speed sensor 72 is attached to the engine 2. The engine speed sensor 72 detects the rotation speed of the engine 2. A crank angle sensor 73 is also attached to the engine 2. The crank angle sensor 73 detects the rotation angle of the crankshaft 21. The air flow sensor 75 is attached to the intake passage 40. The air flow sensor 75 detects the flow rate of fresh air flowing through the intake passage 40.

[0081] The coolant temperature sensor 76 is attached to the engine 2. The coolant temperature sensor 76 detects the temperature of the coolant. The intake air temperature sensor 77 is attached to the intake passage 40. The intake air temperature sensor 77 detects the temperature of fresh air. The exhaust temperature sensor 78 is attached to the exhaust passage 50. The exhaust temperature sensor 78 detects the temperature of exhaust gas discharged from the combustion chamber 23.

[0082] The SCV opening sensor 80 is attached to the SCV 32. The SCV opening sensor 80 detects the opening of the SCV 32. The EGR valve opening sensor 81 is attached to the EGR valve 56. The EGR valve opening sensor 81 detects the opening of the EGR valve 56. The catalyst temperature sensor 82 is attached to the exhaust gas purification device 52. The catalyst temperature sensor 82 detects the temperature of the three-way catalyst.

[0083] These sensors output detection signals to the VCM 13. The VCM 13 processes the input detection signals appropriately and then outputs them to the ECM 11 and the TCM 12 as necessary. As described above, the VCM 13 is configured to be able to electrically communicate with the ECM 11 and the TCM 12. The ECM 11 and the TCM 12 can electrically communicate with each other via the VCM 13.

[0084] The ECM 11 is a module that mainly controls the operation of the engine 2. That is, the ECM 11 is electrically connected to the injection valves 25, the spark plugs 26, the intake S-VT 30, the exhaust S-VT 31, the throttle valve 42, the SCV 32, and the EGR valve 56. The ECM 11 outputs control signals to these components to control their operation.

[0085] The TCM 12 is a unit that mainly controls the operation of the automatic transmission 3. That is, the TCM 12 is electrically connected to the transmission mechanism 63 and the torque converter 62. The TCM 12 outputs control signals to these components to control their operation.

[0086] Based on detection signals input from various sensors, the VCM 13, ECM 11, and TCM 12 that constitute the powertrain control device 10 cooperate with each other to control the engine 2 and the automatic transmission 3. This allows the automobile 1 to run.

[0087] <Engine control> The ECM 11 controls the engine 2 so that power is output in accordance with the driver's request. In the case of the automobile 1, in particular, in order to achieve high-level emission performance, the ECM 11 executes full-range stoichiometric air-fuel ratio operation control, which controls the operation of the engine 2 so that the stoichiometric air-fuel ratio is achieved over the entire operating range.

[0088] As described above, the exhaust gas purification device 52 purifies exhaust gas using a three-way catalyst. To obtain a high purification rate with a three-way catalyst, it is necessary to stabilize the air-fuel ratio at the stoichiometric air-fuel ratio (14.7) or in a narrow range (a so-called window) around it. Therefore, to achieve high-level emissions performance, it is necessary to operate the engine 2 within that window throughout its entire operating range.

[0089] Therefore, even if the engine speed and load change, the ECM 11 controls the air-fuel ratio (A / F) to the stoichiometric air-fuel ratio (λ=1), that is, to stay within the window range (the target air-fuel ratio is always λ1). This allows the exhaust gas purification device 52 to always be kept in an optimal state for purification, thereby achieving high-level emission performance.

[0090] On the other hand, if the stoichiometric air-fuel ratio is used in an operating range where the heat value of exhaust gas is high, such as in an operating range where the engine speed and load are high, the amount of exhaust heat will increase further due to efficient combustion. As a result, the heat value of the exhaust gas will become excessive, and the temperature of the three-way catalyst may exceed the allowable temperature. If the allowable temperature is exceeded, the three-way catalyst will thermally deteriorate and its durability will decrease.

[0091] Therefore, in the case of this automobile 1, an upper limit value for the intake air charge amount is set to prevent the three-way catalyst from exceeding an allowable temperature. Then, when the intake air charge amount reaches the upper limit value, the ECM 11 executes intake air charge amount limiting control to limit the intake air charge amount so that the intake air charge amount does not exceed the upper limit value.

[0092] That is, the ECM 11 cuts off the intake air charge amount (the mass of fresh air charged into the combustion chamber 23 during combustion) that exceeds its upper limit. Because full-range stoichiometric air-fuel ratio operation control is executed, the mass of fuel injected into the combustion chamber 23 also decreases accordingly. Because the heat of combustion is reduced, the temperature of the exhaust gas also drops. Therefore, the three-way catalyst can be prevented from exceeding the allowable temperature.

[0093] The actual intake air charge amount is limited using the charging efficiency (CE), which is a general index of the intake air charge amount. That is, a CE limit value is set corresponding to the upper limit value of the intake air charge amount. The ECM 11 executes intake air charge amount limit control based on the CE limit value (CE limit value). In intake air charge amount limit control, the CE limit value is adjusted so that the temperature of the three-way catalyst does not exceed the allowable temperature.

[0094] In other words, the higher the engine speed and load, the higher the exhaust gas temperature, so the CE limit value becomes stricter (smaller). In particular, the engine speed has a greater effect on the rise in exhaust gas temperature than the load. Therefore, the CE limit value is set to a smaller value as the engine speed increases.

[0095] The CE is affected by dynamic factors such as the pressure and temperature of the air being charged, and static factors such as the piping resistance of the intake passage 40. The CE is an estimated value calculated based on these multiple factors. The accuracy of the CE estimation varies depending on the calculation method. Therefore, in this vehicle 1, a method for calculating the CE limit value has been devised to obtain an appropriate estimation accuracy according to the risk (details will be described later).

[0096] The ECM 11 also performs ignition retard control to suppress knocking. That is, during normal combustion, the ECM 11 controls the spark plug 26 so that ignition occurs at the optimal timing near top dead center. However, when knocking begins to occur, the ECM 11 controls the ignition timing to be retarded (ignition retard control). Retarding the ignition timing suppresses knocking.

[0097] <Automatic transmission control> The TCM 12 controls the automatic transmission 3 to change the output of the engine 2 in accordance with the running state of the automobile 1. A predetermined shift map 90 is pre-installed in the TCM 12. Based on the shift map 90, the TCM 12 executes automatic shift control that automatically controls the operation of the automatic transmission 3.

[0098] An example of the gear shift map 90 is shown in Figure 4. As described above, the automatic transmission 3 has gears from 1st to 6th. The gear shift maps 90 corresponding to upshifts and downshifts are set based on the accelerator opening and vehicle speed.

[0099] The upper diagram is the shift map 90 for upshifting. The lower diagram is the shift map 90 for downshifting. A shift occurs by crossing the boundary between two adjacent gears. For example, in the shift map 90 for upshifting, when the boundary line between fifth and sixth gears is crossed, the TCM 12 executes control to upshift from fifth to sixth gear. In the shift map 90 for downshifting, when the boundary line between fourth and third gears is crossed, the TCM 12 executes control to downshift from fourth to third gear.

[0100] The TCM 12 also executes forced upshift control to forcibly upshift the automatic transmission 3 based on a rev limit to prevent the engine 2 from over-revving. The rev limit is an upper limit of the engine speed that is preset in the TCM 12 to prevent the rotation of the engine 2 from exceeding an allowable limit.

[0101] When the engine speed reaches the rev limit, the TCM 12 forcibly upshifts the automatic transmission 3 in addition to the gear shift based on the above-mentioned shift map 90. When the automatic transmission 3 upshifts, the gear ratio becomes smaller and the engine speed drops. Therefore, the engine speed can be prevented from exceeding the rev limit.

[0102] <Issues with intake air charge limiting control and solutions> When the intake charge amount is restricted, the intake charge amount becomes less than the required amount, which causes a shortage of power from engine 2. As a result, the vehicle speed may not increase even when the driver depresses the accelerator pedal.

[0103] Figure 5A shows an example of the changes over time of the main elements when restricting the intake air charge amount in a conventional manner. The normal rev limit (NE0) is set to a sufficiently large value depending on the performance of the engine 2. When the accelerator is depressed and the engine speed increases, CE increases accordingly.

[0104] At the same time, the heat content of the exhaust gas also increases. Therefore, when operating in the high load and high rotation range, the temperature of the three-way catalyst rises and approaches the allowable temperature. As a result, the CE limit value becomes gradually stricter (smaller).

[0105] As a result, when CE reaches the CE limit value (timing t1), the intake air charge limit control limits CE (intake air charge amount) (CE reaches a plateau at the CE limit value). As a result, the output of engine 2 does not increase any further, so the engine speed also reaches a plateau. The vehicle speed also does not increase.

[0106] Even if the accelerator pedal is depressed further, the engine speed and vehicle speed do not increase. Since the vehicle speed does not change, the automatic transmission 3 does not upshift. Since the vehicle 1 cannot travel in accordance with the driver's operation, the driving performance of the vehicle 1 deteriorates.

[0107] Therefore, the powertrain control device 10 is designed to use a rev limiter so that the vehicle speed increases and the vehicle can travel in accordance with the driver's operation even if the output of the engine 2 is limited. Specifically, when the ECM 11 limits the CE, the TCM 12 executes rev limit change control to lower the rev limit.

[0108] 5B illustrates the time-dependent changes in the main elements when the intake air charge amount is limited by the powertrain control device 10. As in the past, when the accelerator is depressed and the engine speed increases, the CE also increases. When the vehicle is driven in the high-load and high-speed range, the CE limit value gradually becomes stricter (smaller).

[0109] As a result, when CE reaches the CE limit value (timing t1), CE is limited by intake air charge limit control. At that time, in this powertrain control device 10, the TCM 12 executes rev limit change control to lower the rev limit by a predetermined amount.

[0110] In addition to the normal rev limit, the ECM 11 also has a temporary rev limit set. An example of this is shown in a rev limit table in FIG. 6. The original rev limit, which corresponds to the allowable limit of engine speed, does not need to be differentiated between high and low gear positions. Therefore, in this powertrain control device 10, a first rotation speed (NE0) common to first through sixth gears is set as the normal rev limit (RL-nor).

[0111] On the other hand, the rev limit used for rev limit change control (temporary rev limit: RL-temp) is set differently depending on the gear. Specifically, the amount of reduction from the normal rev limit in the temporary rev limit is greater in higher gears than in lower gears.

[0112] In the case of the temporary rev limit illustrated, a common second engine speed (NE2) is set for the low gears from 1st to 3rd, and a common third engine speed (NE3) is set for the high gears from 4th to 6th. The second engine speed is higher than the third engine speed, and the first engine speed is sufficiently higher than the second engine speed (NE0>>NE2>NE3). Note that, as shown in a modified example described later, the engine speed of the temporary rev limit does not have to be set separately for the low gear and the high gear. It may be set differently for each gear, or may be set arbitrarily for the low gear, the medium gear, the high gear, etc.

[0113] By setting a temporary rev limit higher in the lower gears than in the higher gears, the upper limit of engine speed becomes relatively higher in the lower gears, which makes it possible to increase vehicle speed to a higher speed more quickly in the lower gears.

[0114] 5B, the TCM 12 executes rev limit change control to switch the normal rev limit to a temporary rev limit. At this time, if the automatic transmission 3 is in second gear, the execution of the rev limit change control sets the second engine speed (NE2) as the temporary rev limit.

[0115] The second rotation speed (NE2) is the rotation speed that can be achieved in second gear when CE is limited. The second rotation speed (NE2) is also the rotation speed that can be achieved in first and third gear when CE is limited. Similarly, the third rotation speed (NE3) is the rotation speed that can be achieved in fourth to sixth gear when CE is limited.

[0116] When the engine speed reaches the second speed (NE2), the TCM 12 executes forced upshift control to forcibly upshift the automatic transmission 3. The automatic transmission 3 shifts from second gear to third gear. This reduces the gear ratio of the automatic transmission 3 and reduces the engine speed. The vehicle speed is maintained.

[0117] Furthermore, as the engine speed decreases, the CE restriction is relaxed. That is, the CE restriction value increases. This allows the engine 2 to obtain power, and the engine speed and vehicle speed increase. Then, when the engine speed reaches the second speed (NE2) (at time t2), the TCM 12 again executes forced upshift control, forcibly upshifting the automatic transmission 3. The automatic transmission 3 shifts from third gear to fourth gear.

[0118] As a result, the engine speed decreases and the CE limit value increases. Engine 2 is able to obtain power again, and the engine speed and vehicle speed increase. This state change is repeated until the highest gear, sixth gear, is reached. As a result, it becomes possible to obtain power from engine 2 with each upshift in response to accelerator operation, and vehicle speed can be increased continuously.

[0119] Therefore, the vehicle can travel in accordance with the driver's operation. This can prevent the deterioration of the driving performance of the vehicle 1. However, even with this improvement, the power of the engine 2 itself is limited. Therefore, it cannot be denied that the increase in vehicle speed is relatively gradual.

[0120] <Specific control examples of powertrain control devices> Fig. 7 shows a flowchart relating to full-range stoichiometric air-fuel ratio operation control. Fig. 8 shows a flowchart relating to intake air charge amount limiting control. Fig. 9A and Fig. 9B show flowcharts relating to forced upshift control and rev limit changing control.

[0121] 7, the VCM 13 constantly reads detection signals output from various sensors while the engine 2 is running (step S1). The ECM 11, in cooperation with the VCM 13, sets a torque (target output) to be output as a target in controlling the engine 2 based on these detection signals (step S2). The ECM 11 sets a target CE (target CE) corresponding to the stoichiometric air-fuel ratio (λ1) based on the target output (step S3).

[0122] The ECM 11 sets the throttle opening based on the target CE (step S4). The ECM 11 sets the fuel injection amount corresponding to the stoichiometric air-fuel ratio (λ1) (step S5). The ECM 11 sets the timing of fuel injection and ignition for each cylinder 20 according to the operating state of the engine 2 (step S6). The ECM 11 controls the operation of the throttle valve 42, the injector 25, and the spark plug 26 based on the set throttle opening, fuel injection amount, and fuel injection and ignition timing (step S7). As a result, combustion occurs intermittently and repeatedly in the combustion chamber 23 of each cylinder 20.

[0123] Through such control by the powertrain control device 10, the engine 2 operates at the stoichiometric air-fuel ratio throughout its entire operating range. Therefore, exhaust gas can be purified in an optimal state at all times. Advanced emissions performance can be achieved. The ECM 11 also controls the operation of the intake S-VT 30, exhaust S-VT 31, SCV 32, and EGR valve 56 in accordance with the operating state of the engine 2, in conjunction with the operation of the throttle valve 42, etc.

[0124] On the other hand, if the powertrain control device 10 executes such full-range stoichiometric air-fuel ratio operation control, as described above, the amount of exhaust heat from the engine 2 will be excessive in the high rotation speed and high load operation range. Therefore, the ECM 11 sets a CE limit value according to the risk so as to prevent the temperature of the three-way catalyst from exceeding the allowable temperature.

[0125] Specifically, as shown in Fig. 8, the ECM 11, in cooperation with the VCM 13, acquires the temperature Texg of the exhaust gas flowing out from the engine 2. Then, it determines whether or not the temperature of the exhaust gas is higher than a predetermined first threshold value Ts1. Furthermore, the ECM 11, in cooperation with the VCM 13, acquires the temperature Tcat of the three-way catalyst. Then, it determines whether or not the temperature of the three-way catalyst is higher than a predetermined second threshold value Ts2 (step S10). Note that these first and second threshold values ​​are preset in the ECM 11.

[0126] If the ECM 11 determines that the exhaust gas temperature is equal to or lower than the first threshold and that the three-way catalyst temperature is equal to or lower than the second threshold, the ECM 11 determines that the three-way catalyst temperature is unlikely to exceed the allowable temperature (low risk state), and then calculates the CE limit value (first CE limit value) using a normal simple calculation method (first calculation method) (step S11).

[0127] On the other hand, if the ECM 11 determines that the temperature of the exhaust gas is higher than the first threshold or that the temperature of the three-way catalyst is higher than the second threshold, the ECM 11 determines that the temperature of the exhaust gas or the three-way catalyst is approaching its limit and that there is a high possibility that the temperature of the three-way catalyst will exceed the allowable temperature (high risk state). As a result, the ECM 11 switches the calculation method and calculates the CE limit value (second CE limit value) using a temporary advanced calculation method (second calculation method) (step S12).

[0128] The first and second calculation methods have different estimation accuracy for the CE limit value. The second calculation method has higher estimation accuracy than the first calculation method. The second CE limit value is more reliable as a CE limit value than the first CE limit value.

[0129] In the case of a low-risk state, the CE usually deviates from the CE limit value. In other words, the CE rarely reaches the CE limit value. Therefore, there is no particular problem even if the estimation accuracy is not high.

[0130] On the other hand, in a high-risk state, the CE typically reaches the CE limit value and is limited (the intake air charge amount is limited). This reduces the output of the engine 2, which affects the driving performance of the automobile 1. Therefore, in order to suppress the reduction in the output of the engine 2, it is preferable that the reliability of the CE limit value is high.

[0131] Of the various state values ​​that are actually measured, the CE limit value has a high correlation with the engine speed, intake air temperature, and coolant temperature of the engine 2. Fig. 10 illustrates an example of the relationship between these state values ​​and the CE limit value.

[0132] As the engine speed increases, the amount of exhaust heat from the engine 2 per unit time increases, causing the temperature of the three-way catalyst to rise. Therefore, as the engine speed increases, the CE limit value (upper limit of the intake air charge amount) becomes smaller, i.e., the CE limit is set to become stricter.

[0133] The same applies to the intake air temperature and the coolant temperature of the engine 2. The CE limit value is set to be smaller as the intake air temperature increases. The CE limit value is set to be smaller as the coolant temperature of the engine 2 increases.

[0134] In this way, it is preferable to set the CE limit value smaller as at least one of the rotation speed, intake air temperature, and coolant temperature of the engine 2 increases, which allows a good balance between suppressing thermal deterioration of the three-way catalyst and suppressing a decrease in the output of the engine 2.

[0135] In particular, the temperature of the three-way catalyst is more dependent on the engine speed and intake air temperature than on the coolant temperature of the engine 2. Therefore, in the first calculation method, the first CE limit value is calculated based on two of these state values, the engine speed and the intake air temperature, and a predetermined reference state value.

[0136] The ECM 11 is equipped with a base map that contains data representing standard values ​​of other state values ​​required for CE calculation (e.g., SCV opening, intake and exhaust S-VT angles, etc.). The standard state value is obtained from the base map. According to the first calculation method, which performs calculation based on two main state values, a first CE limit value that is necessary and sufficiently reliable can be calculated efficiently with simple calculations.

[0137] On the other hand, in the second calculation method, the CE limit value (base value) is calculated in the same manner as in the first calculation method, based on three values ​​consisting of the engine speed, intake air temperature, and coolant temperature of the engine 2, and predetermined reference state values ​​obtained from the base map. According to the second calculation method, the CE limit value (base value) is calculated based on all three state values ​​that are highly correlated, so a higher degree of estimation accuracy can be obtained.

[0138] In the second calculation method, in order to further improve the estimation accuracy, the CE limit value (base value) is further corrected according to the actually measured state value, thereby calculating a more reliable second CE limit value.

[0139] In the case of this automobile 1, the state values ​​that affect the estimation accuracy include the SCV opening, intake S-VT angle, exhaust S-VT angle, EGR rate, and retard amount. Figure 11 shows an example of the relationship between these state values ​​and the correction value.

[0140] For example, in the case of the SCV opening, the reference state value (BS value) is set to full open (100% opening). As the SCV 32 opening deviates from this value, that is, as the SCV opening decreases, the intake air introduced into the combustion chamber 23 from the pair of intake ports 2c, 2c becomes more uneven. This increases the variation in the amount of fresh air in the combustion chamber 23, which reduces the accuracy of CE calculation. Therefore, the deviation from the CE limit value (base value) increases.

[0141] Therefore, the smaller the SCV opening, the larger the correction value is set. The CE limit value (base value) becomes stricter based on the correction value, that is, it is corrected to become smaller. This increases the reliability of the CE limit value.

[0142] For the S-VT angles of the exhaust and intake, a predetermined angle α is set as the reference state value (BS value). The greater the deviation of the opening and closing timing from this angle, i.e., the greater the deviation Δα from this angle, the greater the variation in the amount of fresh air in the combustion chamber 23. The accuracy of the CE calculation decreases, and the deviation from the CE limit value (base value) increases.

[0143] Therefore, the correction value is set to increase as the S-VT angle deviation Δα increases. The CE limit value (base value) is corrected to be stricter, that is, smaller, based on the correction value.

[0144] The EGR rate is set to a predetermined value β as its reference state value (BS value). When the opening of the EGR valve 56 is adjusted and the EGR rate changes to the negative side, the amount of fresh air in the combustion chamber 23 increases relatively. Therefore, CE becomes larger than the reference state value.

[0145] Therefore, the correction value is set to be larger as the deviation Δβ in the EGR rate becomes larger on the negative side, corresponding to the deviation amount of the opening degree of the EGR valve 56. The CE limit value (base value) is corrected to be stricter, that is, smaller, based on the correction value.

[0146] The retard amount is set to a predetermined value γ that is more retarded than MBT as its reference state value (BS value). Therefore, when the retard amount increases, the combustion timing is delayed, and the temperature of the exhaust gas emitted from the engine 2 increases.

[0147] Therefore, the correction value is set to be larger as the retard amount deviation Δγ becomes larger. The CE limit value (base value) is corrected to be stricter, that is, smaller, based on the correction value.

[0148] In this way, the second calculation method obtains a second CE limit value that takes into account the decrease in CE calculation accuracy and the difference between the reference state value and the actual state value. The second calculation method can calculate CE with a high degree of estimation accuracy and can calculate a highly reliable second CE limit value. Note that the state values ​​considered for correction in the second calculation method, their reference state values, and how to handle the correction values ​​can be changed as appropriate depending on the specifications.

[0149] As shown in FIG. 8, when it is determined that the state is a high-risk state, the ECM 11 calculates the second CE limit value and transmits a command to the TCM 12 to change the CE limit flag (flag change command) (step S13).

[0150] As shown in Fig. 9A, the TCM 12 sets the initial value of the CE restriction flag to "0" (step S20). The value of the CE restriction flag is either "0" or "1." "0" corresponds to a low risk state, and "1" corresponds to a high risk state.

[0151] The TCM 12 determines whether or not a flag change command has been received from the ECM 11 (step S21). If a flag change command has not been received (No in step S21), the vehicle is in a low-risk state, so the TCM 12 refers to a rev limit table and sets a normal rev limit (RL-nor) according to the gear position (step S22). In the case of this vehicle 1, a uniform value (NE0) is set regardless of the gear position.

[0152] If the state is low risk, the TCM 12 determines whether the engine speed (NE) exceeds the normal rev limit (step S23). If the engine speed is equal to or lower than the normal rev limit, the TCM 12 automatically shifts gears (step S24). That is, the TCM 12 switches the gear position of the automatic transmission 3 based on the shift map 90, as in the conventional case.

[0153] On the other hand, if the engine speed exceeds the normal rev limit, the TCM 12 determines whether the automatic transmission 3 is in the highest gear (sixth gear in this vehicle 1) (step S25). If the automatic transmission 3 is not in the highest gear, the TCM 12 forcibly shifts up (step S26).

[0154] The automatic transmission 3 is forced to upshift, which reduces the engine speed. This allows the engine speed to be set lower than the normal rev limit value, preventing the engine 2 from over-revving.

[0155] After the forced upshift, the TCM 12 returns. On the other hand, if the highest gear is selected, upshifting is not possible. Therefore, in this case, the TCM 12 also returns. The powertrain control device 10 prevents over-revving of the engine 2 by means other than the forced upshift (for example, by cutting fuel).

[0156] If the TCM 12 receives a flag change command from the ECM 11, the state is high risk (Yes in step S21). Therefore, in this case, as shown in FIG. 9B, the TCM 12 changes the value of the CE restriction flag from "0" to "1" (step S30).

[0157] Then, the TCM 12 refers to the rev limit table and sets a temporary rev limit (RL-temp) according to the gear position (step S31). In the case of this automobile 1, a value (NE2) for a low gear position is set for first to third gear positions, and a value (NE3) for a high gear position is set for fourth to sixth gear positions.

[0158] Then, the TCM 12 determines whether the engine speed (NE) exceeds the temporary rev limit (step S33). If the engine speed is equal to or less than the temporary rev limit, the TCM 12 automatically shifts gears unless the engine speed exceeds the temporary rev limit (step S34).

[0159] When the engine speed exceeds the temporary rev limit, the TCM 12 determines whether the automatic transmission 3 is in the highest gear (step S35). If the automatic transmission 3 is not in the highest gear, the TCM 12 forcibly upshifts (step S36).

[0160] The automatic transmission 3 is forced to upshift, which reduces the engine speed. The reduction in engine speed relaxes and increases the CE limit value. This allows the engine 2 to obtain power, which increases the engine speed and vehicle speed.

[0161] Then, the TCM 12 changes the rev limit from the temporary rev limit to the normal rev limit (step S37). The TCM 12 also resets the value of the CE restriction flag to its initial value (step S38). After that, the TCM 12 returns.

[0162] Therefore, this powertrain control device 10 executes intake air filling amount limiting control, which allows full-range stoichiometric air-fuel ratio operation while maintaining the three-way catalyst at an appropriate temperature. Furthermore, even when intake air filling limiting control is executed, the power of the engine 2 can be secured by combining forced upshift control and rev limit change control. A decrease in vehicle driving performance due to insufficient engine output can also be suppressed.

[0163] This enables advanced emissions performance in gasoline engine vehicles without compromising driving performance.

[0164] <Modification> When the above-described control is performed, if the automobile 1 is accelerated while the engine 2 is running at high speed and under high load, the engine noise may be perceived as noisy in response to acceleration.

[0165] That is, when a forced upshift is performed by rev limit change control, the power of the engine 2 itself is limited as described above, so the increase in vehicle speed, i.e., acceleration, is unavoidably gradual. For this reason, for example, when traveling at high speed on a long, hilly lane, even if the accelerator is fully opened while the engine 2 is operating at high speed, sufficient acceleration may not be obtained despite the loud engine noise.

[0166] An example of simplified driving data from a test run of a vehicle (hereinafter referred to as a test vehicle) to which the disclosed technology is applied is shown in Figure 12. The example driving data was obtained when the test vehicle was traveling at high speed (e.g., 140 km / h) on a long, uphill lane and the accelerator pedal was depressed to full throttle in order to accelerate.

[0167] In the case of this test vehicle, the gear stage when the accelerator is fully opened in this driving state is 4th gear, and as the accelerator opening increases, the automatic transmission 3 shifts down to accelerate. The gear stage is changed to 6th gear, 5th gear, and 4th gear.

[0168] As the throttle opening increases, the engine speed and vehicle speed gradually increase. As the engine speed increases, the engine noise becomes louder. Then, at timing t2, a forced upshift is performed by rev limit change control, and the automatic transmission 3 switches from fourth gear to fifth gear.

[0169] During acceleration in fourth gear, the torque (load) of engine 2 decreases due to the CE limit, as indicated by arrow A2. Accordingly, in the latter half of fourth gear, the increase in engine speed becomes gradual, the acceleration of the test vehicle becomes smaller, and the increase in vehicle speed also becomes gradual (engine speed r1, after time t1).

[0170] In such a case, the engine noise is loud and annoying, but the driver may not be able to achieve the desired acceleration, and may feel that the acceleration is sluggish. Therefore, in this modified example (the second powertrain control device 10), the engine noise can be suppressed even in such a case, and the driver may not feel that the acceleration is sluggish.

[0171] (Configuration of the second powertrain control device) The basic configuration of the second powertrain control device 10 is the same as that of the above-described powertrain control device 10 (herein referred to as the first powertrain control device 10). For example, like the first powertrain control device 10, the second powertrain control device 10 also includes an ECM 11, a TCM 12, a VCM 13, etc., and has the same basic configuration.

[0172] Therefore, the same reference numerals will be used for the same components and the description thereof will be simplified or omitted. The components with different contents will be described in detail.

[0173] In the second powertrain control device 10, when the TCM 12 executes the rev limit change control, if the acceleration of the automobile 1 is equal to or less than a preset acceleration feeling discrimination boundary value, the second powertrain control device 10 is configured to execute control (early forced upshift control) to forcibly upshift the automatic transmission 3 when the engine speed reaches a predetermined value lower than the temporary rev limit set by the rev limit change control.

[0174] FIG. 13 shows an example of a time chart of the early forced upshift control. The time chart shown here corresponds to the driving data of the test vehicle described above. That is, in this time chart, the driving data described above is used as a comparative example before the modification. The two-dot chain line corresponds to the driving data of the test vehicle described above. The solid line corresponds to the early forced upshift control of this modified example.

[0175] As described above, in the comparative example, the driver begins to feel a sense of sluggish acceleration at engine speed r1 and time t1. Then, at time t2, a forced upshift is performed at temporary rev limit r2 by rev limit change control, and the automatic transmission 3 is switched from fourth gear to fifth gear.

[0176] In the second powertrain control device 10, the early forced upshift control forcibly shifts up (from fourth gear to fifth gear) when the engine speed reaches a predetermined engine speed r3 that is lower than the temporary rev limit r2, as shown by arrow A2 in FIG. 13. As a result, the engine speed drops at an early timing, as shown by arrow A3 in FIG. 13. Accordingly, the engine noise becomes quieter. Therefore, the driver is less likely to perceive the engine noise as annoying.

[0177] However, if the driver can sense the acceleration, there is no risk of the driver feeling a sense of sluggish acceleration even if the engine noise is noisy. Therefore, it is preferable to upshift when the driver can no longer sense the acceleration. In contrast, the second powertrain control device 10 sets a boundary value (acceleration sense discrimination boundary value: a1) of the range of acceleration at which the driver can sense the acceleration, depending on the driving state of the vehicle. The acceleration sense discrimination boundary value a1 can be set in advance by conducting tests, simulations, etc.

[0178] If the acceleration of the vehicle is higher than the threshold for discriminating between acceleration sensations, the driver can feel the acceleration, but if it falls below that threshold, the driver will not feel the acceleration. In Figure 13, a forced upshift occurs when the acceleration of the vehicle reaches the threshold for discriminating between acceleration sensations (timing t3). This effectively prevents the driver from feeling a sluggish acceleration sensation.

[0179] However, when the automatic transmission 3 upshifts, the gear ratio becomes smaller and the acceleration decreases. Therefore, even if the engine noise is reduced by forcibly upshifting early, if the vehicle stalls after upshifting, it may cause discomfort to the driver. Therefore, it is preferable to maintain the acceleration state even after upshifting.

[0180] Therefore, the second powertrain control device 10 is configured to execute early forced upshift control only when the acceleration of the vehicle after upshifting is predicted to be equal to or greater than a preset stall sensation identification boundary value.

[0181] Specifically, a boundary value of the range of acceleration at which the driver can sense a stall (stall sense discrimination boundary value: a2) is set in the second powertrain control device 10 according to the driving state of the vehicle. The stall sense discrimination boundary value a2 is essentially "0 (zero)," but is set to a positive value (e.g., 0.05 m / s2) to allow for practical error. The stall sense discrimination boundary value a2 can also be set in advance by conducting tests, simulations, etc.

[0182] In Figure 13, the set acceleration before upshifting (acceleration in fourth gear) is shown by a solid line, and the set acceleration after upshifting (acceleration in fifth gear) is shown by a dashed line. The rate of decrease in acceleration is smaller after upshifting than before upshifting (the slope is gentler). As a result, the magnitudes of the two accelerations are reversed around timing t2, making it possible to increase vehicle speed through forced upshift control.

[0183] At the timing t3 when the early forced upshift control is executed, the acceleration after the upshift is sufficiently higher than the stall feeling identification threshold value a2. Therefore, the acceleration state can be maintained even after the upshift. There is no risk that the driver will feel a sluggish acceleration.

[0184] The early forced upshift control is executed only when the engine speed is a predetermined high speed in a specific gear position of the automatic transmission 3.

[0185] That is, as described above, the early forced upshift control is effective in the case of a specific gear position and engine speed where the driver feels a sense of sluggish acceleration in response to a loud engine noise due to the execution of the forced upshift control. The conditions vary depending on the specifications of the vehicle.

[0186] In the example vehicle, as described above, the engine speed r3 in fourth gear meets this condition, but there may also be cases where a predetermined engine speed such as third gear, fifth gear, or both third and fourth gears meets this condition, provided that the engine speed is higher than a predetermined speed (for example, 4000 rpm or higher).

[0187] Although the early forced upshift is preferably performed at or below the acceleration feeling discrimination threshold value a1, it may be performed at a timing higher than the acceleration feeling discrimination threshold value a1. For example, the early forced upshift control may be performed when the engine speed reaches r1 or immediately thereafter.

[0188] (Example of second powertrain control device) 14 shows an example of a table of rev limits set in the second powertrain control unit 10. In the second powertrain control unit 10, as in the first powertrain control unit 10, a normal rev limit (RL-nor) is set.

[0189] The first powertrain control device 10 sets a temporary rev limit (RL-temp) consisting of two rotation speeds, a low speed and a high speed. In contrast, the second powertrain control device 10 sets a temporary first rev limit (RL-temp1) corresponding to the temporary rev limit (RL-temp), as well as a temporary second rev limit (RL-temp2) used for early forced upshift control.

[0190] In the example table, a temporary first rev limit (RL-temp1) with a different engine speed is set for each gear (NE11 to NE16). As with the temporary rev limit (RL-temp) described above, the first engine speed (NE0) of the normal rev limit (RL-nor) is significantly higher than the engine speeds of these temporary first rev limits (RL-temp1) (NE0>>NE1*).

[0191] As with the temporary rev limit (RL-temp) mentioned above, the amount of reduction in the temporary first rev limit from the normal rev limit is the same for adjacent gears, or is greater for higher gears than for lower gears. In other words, the relationship between the engine speeds of these temporary first rev limits (RL-temp1) is NE11 ≥ NE12 ≥ NE13 ≥ NE14 ≥ NE15 ≥ NE16.

[0192] This rev limit table also corresponds to the driving data described above. That is, a temporary second rev limit (RL-temp2) is set for fourth gear of the automatic transmission 3. The engine speed NE24 is smaller than the engine speed NE14 of the corresponding temporary first rev limit (RL-temp1) for fourth gear (NE14>NE24).

[0193] Here, an example is given of setting a temporary second rev limit (RL-temp2) only in fourth gear, but as mentioned above, depending on the specifications of the vehicle, a temporary second rev limit (RL-temp2) may also be set in third gear (NE23).

[0194] (Specific control example of the second powertrain control device) The second powertrain control device 10 also has the same basic configuration as the first powertrain control device 10 regarding the forced upshift control and the rev limit change control, except for the early forced upshift control.

[0195] That is, the portion shown in Figure 9A is the same in the flowchart of the second powertrain control device 10. In the flowchart of the second powertrain control device 10, a portion of the portion shown in Figure 9B is different. Therefore, for steps with the same content, the same reference numerals are used, and the explanation of the content is simplified or omitted.

[0196] In the flowchart of the second powertrain control device 10, when the TCM 12 receives a flag change command from the ECM 11, the TCM 12 changes the value of the CE restriction flag from "0" to "1" (step S30), as shown in FIG.

[0197] Then, the TCM 12 refers to the rev limit table (see FIG. 14) and sets temporary rev limits (RL-temp1 and RL-temp2) according to the gear position (step S31). In the case of the second powertrain control device 10, the engine speed values ​​(NE11 to NE16) corresponding to each of the first to sixth gear positions are set as the temporary first rev limit (RL-temp1). The engine speed value (NE24) corresponding to fourth gear position is set as the temporary second rev limit (RL-temp2).

[0198] Then, the TCM 12 determines whether the engine speed (NE) exceeds the temporary first rev limit (RL-temp1) (step S33). If the engine speed exceeds the temporary first rev limit (Yes in step S33), the TCM 12 determines whether the automatic transmission 3 is in the highest gear (step S35). If the automatic transmission 3 is not in the highest gear, the TCM 12 forcibly upshifts (step S36).

[0199] The automatic transmission 3 is forced to upshift, which reduces the engine speed. The reduction in engine speed relaxes and increases the CE limit value. This allows the engine 2 to obtain power, which increases the engine speed and vehicle speed.

[0200] Then, the TCM 12 changes the rev limit from the temporary first rev limit to the normal rev limit (step S37). The TCM 12 also resets the value of the CE restriction flag to its initial value (step S38). After that, the TCM 12 returns.

[0201] On the other hand, if the engine speed is equal to or lower than the temporary first rev limit (No in step S33), the TCM 12 determines whether the gear position of the automatic transmission 3 is a gear position that is a target for early forced upshift control (step S39). Specifically, it determines whether the gear position is fourth gear.

[0202] As a result, if the gear position of the automatic transmission 3 is not fourth (No in step S39), the TCM 12 maintains the automatic shift (step S40), changes the rev limit from the temporary first rev limit to the normal rev limit (step S37), resets the value of the CE restriction flag to the initial value (step S38), and returns.

[0203] On the other hand, if it is determined that the gear position of the automatic transmission 3 is fourth (Yes in step S39), the TCM 12 determines whether the engine speed (NE) exceeds the temporary second rev limit (RL-temp2) (step S41). As a result, if the engine speed (NE) exceeds the temporary second rev limit (RL-temp2) (Yes in step S41), the TCM 12 may immediately execute early forced upshift control, as indicated by the two-dot chain line.

[0204] However, in the case of the second powertrain control device 10, emphasis is placed on driving performance, and the TCM 12 compares the acceleration of the automobile 1 with the acceleration feeling discrimination boundary value a1 (step S42). As a result, if the acceleration of the automobile 1 is higher than the acceleration feeling discrimination boundary value a1 (No in step S42), the TCM 12 proceeds to step S40 to maintain automatic shifting, since the acceleration feeling is obtained.

[0205] On the other hand, if the acceleration of the automobile 1 is equal to or less than the acceleration feeling discrimination boundary value a1 (Yes in step S42), the TCM 12 may immediately execute early forced upshift control as shown by the two-dot chain line, but in the case of this second powertrain control device 10, emphasis is placed on driving performance and a prediction is made as to whether the acceleration after the automobile's upshift will be equal to or greater than the stall feeling discrimination boundary value a2 (step S43).

[0206] As a result, if it is predicted that the acceleration of the automobile 1 after upshifting will not be equal to or greater than the stall feeling identification boundary value a2 (No in step S43), the TCM 12 proceeds to step S40 to maintain automatic shifting, since no acceleration feeling will be obtained even if the vehicle 1 is upshifted.

[0207] On the other hand, if it is predicted that the acceleration of the vehicle 1 after upshifting will be equal to or greater than the stall feeling identification boundary value a2 (Yes in step S43), the TCM 12 executes early forced upshift control because the acceleration feeling can be obtained even if the vehicle 1 upshifts. That is, if the vehicle 1 is not in the highest gear, the TCM 12 performs a forced upshift at an early timing when the engine speed is lower than the temporary first rev limit (step S36).

[0208] As a result, as shown in FIG. 13, the engine speed decreases at an earlier timing. Accordingly, the engine noise also decreases, and the engine noise can be suppressed. The acceleration of the automobile 1 can also be kept within a range that allows the driver to get a sense of acceleration. Therefore, there is no risk that the driver will feel a sense of sluggish acceleration.

[0209] The disclosed technology is not limited to the above-described embodiment, but includes various other configurations. For example, although the embodiment illustrates a vehicle driven only by the engine 2, the vehicle may be a hybrid vehicle that also uses a motor for drive. There may be situations in which a hybrid vehicle cannot use a motor. [Explanation of symbols]

[0210] 1. Automobiles (vehicles) 2 engines 3. Automatic transmission 10 Powertrain control device 11 ECM 12 TCM 13 VCM 20 cylinders 21 Crankshaft 22 Piston 23 Combustion chamber 25 injection valve 26 Spark plug 27 Intake valve 28 Exhaust valve 30 Intake S-VT 31 Exhaust S-VT 32 Swirl control valve (SCV) 33 Cooling water passage 40 intake passage 42 Throttle valve 50 Exhaust passage 51 Muffler 52 Exhaust gas purification device 55 EGR passage 56 EGR valve 62 Torque converter 63 Transmission mechanism 63a Planetary gear mechanism 63b Clutch 70 Accelerator opening sensor 71 Vehicle speed sensor 72 Engine speed sensor 73 Crank angle sensor 75 Airflow sensor 76 Coolant temperature sensor 77 Intake air temperature sensor 78 Exhaust gas temperature sensor 80 SCV opening sensor 81 EGR valve opening sensor 82 Catalyst temperature sensor 90 gear shift map

Claims

1. A powertrain control device for a vehicle including an engine that runs by burning gasoline, an exhaust gas purification device that purifies exhaust gas emitted from the engine using a three-way catalyst, and an automatic transmission that automatically changes the output of the engine, the powertrain control device controlling the engine and the automatic transmission to run the vehicle, an engine control unit that executes a full-range stoichiometric air-fuel ratio operation control that controls the operation of the engine so that the stoichiometric air-fuel ratio is maintained throughout the entire operating range, and also executes an intake air filling amount limiting control that limits the intake air filling amount when the intake air filling amount reaches an upper limit value that is set so that the temperature of the three-way catalyst does not exceed an allowable temperature; a transmission control unit that executes automatic shift control to control the operation of the automatic transmission based on a shift map that is set based on an accelerator opening and a vehicle speed, and that executes forced upshift control to forcibly upshift the automatic transmission when the engine speed reaches a rev limit that is set so that the engine speed does not exceed an allowable limit; and A powertrain control device in which, when the engine control unit limits the intake air filling amount, the transmission control unit executes rev limit change control to lower the rev limit.

2. 2. The powertrain control device according to claim 1, A powertrain control device in which the amount of reduction of the rev limit in the rev limit change control is set to differ depending on the high and low gear stages of the automatic transmission, and the amount of reduction is larger for high gear stages than for low gear stages.

3. 3. The powertrain control device according to claim 1, The powertrain control device is configured such that the upper limit value of the intake air filling amount is set smaller as at least one of the engine speed, the intake air temperature, and the engine coolant temperature increases.

4. 4. The powertrain control device according to claim 3, When it is determined that there is a high possibility that the temperature of the three-way catalyst will exceed the allowable temperature, the powertrain control device calculates an upper limit value of the intake air filling amount based on three values ​​consisting of the engine speed, the intake air temperature, and the engine coolant temperature, and a predetermined reference state value.

5. 5. The powertrain control device according to claim 4, When it is determined that the temperature of the three-way catalyst is unlikely to exceed the allowable temperature, the powertrain control device calculates an upper limit value of the intake air filling amount based on two values ​​consisting of the engine speed and the intake air temperature and a predetermined reference state value.

6. 5. The powertrain control device according to claim 4, The engine has a swirl control valve that changes the strength of a swirl flow generated in a combustion chamber by adjusting the opening degree of the swirl control valve, a powertrain control device that corrects the upper limit of the intake air filling amount based on the deviation of the opening of the swirl control valve from the reference state value;

7. 5. The powertrain control device according to claim 4, The engine has a variable valve timing mechanism that enables adjustment of the opening and closing timing of the intake valve and / or the exhaust valve, A powertrain control device that corrects an upper limit value of the intake air filling amount based on a deviation amount of the opening / closing timing of the intake valve and / or the exhaust valve from the reference state value.

8. 5. The powertrain control device according to claim 4, the engine has an EGR valve that changes the amount of recirculated exhaust gas by adjusting its opening degree; A powertrain control device that corrects the upper limit value of the intake air filling amount based on the deviation amount of the opening of the EGR valve from the reference state value.

9. 5. The powertrain control device according to claim 4, the engine control unit further executes ignition retard control to retard ignition timing in order to suppress knocking, A powertrain control device that corrects the upper limit value of the intake air filling amount based on the retard amount of the ignition timing relative to the reference state value.

10. 2. The powertrain control device according to claim 1, a powertrain control device that, when the transmission control unit executes the rev limit change control, if the acceleration of the vehicle is equal to or less than a preset acceleration feeling discrimination boundary value, executes early forced upshift control to forcibly upshift the automatic transmission when the vehicle reaches a predetermined engine speed that is lower than a temporary rev limit set by the rev limit change control.

11. The powertrain control device according to claim 10, A powertrain control device that executes the early forced upshift control only when the acceleration of the vehicle after the upshift is predicted to be equal to or greater than a preset stall feeling identification boundary value.

12. The powertrain control device according to claim 10 or 11, The powertrain control device is configured such that the early forced upshift control is executed only when the engine speed is a predetermined high speed in a specific gear position of the automatic transmission.

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