JP7380367B2 - engine control device - Google Patents

Description

The present invention relates to an engine control device that performs torque control using a torque demand method.

As seen in Patent Document 1, an engine control device that performs torque control using a torque demand method is known. In engine torque control using the torque demand method, the throttle opening is controlled in order to achieve a target torque, which is a target value of engine torque set based on the amount of accelerator pedal operation, engine speed, and vehicle driving conditions. be exposed. Specifically, the engine load factor required to achieve the target torque is calculated as the value of the requested load factor, and the throttle opening is controlled to an opening that provides a load factor equivalent to the value of the requested load factor. . Note that during the intake response delay period after changing the throttle opening until the load factor changes to a value corresponding to the changed opening, the actual torque of the engine and the target torque deviate. Therefore, in the torque demand method of torque control, the deviation of the actual torque from the target torque is suppressed by adjusting the torque by adjusting the ignition timing etc. according to the deviation between the actual load factor determined from the air flow meter output and the required load factor. There is.

Note that the maximum load factor, which is the load factor when the throttle opening is set to the maximum opening, which is the maximum value of the control range, is a value that changes depending on the engine rotation speed. Therefore, in the current operating state, the maximum torque, which is the maximum value in the range of engine torque that can be adjusted by controlling the throttle opening, is also a value that changes depending on the engine rotation speed. Even if a value exceeding the maximum torque is set as the target torque, it will not be possible to achieve it. Therefore, in torque demand-based torque control, the maximum load factor at the current engine speed is determined, and the upper limit of the target torque is guarded so that the value is equal to or less than the maximum torque determined from the maximum load factor.

Japanese Patent Application Publication No. 2009-185665

By the way, when controlling the throttle opening degree, the following value is set as the value of the target opening degree which is the control target value of the throttle opening degree. That is, when the required load factor is greater than or equal to the maximum load factor, the maximum opening degree is set as the value of the target opening degree. In addition, if the requested load factor is less than the maximum load factor, if the requested load factor decreases from the maximum load factor, the requested load factor will change from the maximum opening degree, which is the value when the requested load factor is the maximum load factor. The target opening degree is set as a value that decreases as the rate decreases.

On the other hand, when looking only at throttle opening control, it is desirable to set a value different from the actual maximum load factor at the current engine speed as the maximum load factor used to calculate the target opening. There are cases. For example, if the target opening is calculated using a value smaller than the actual value for the maximum load factor, the required load factor for which the maximum opening is set as the target opening will be a value smaller than the actual maximum load factor. Become. In such a case, when accelerating the vehicle by depressing the accelerator pedal, the throttle opening will reach its maximum opening earlier, improving the response of the vehicle during acceleration. However, if a value different from the actual value is set as the value of the maximum load factor, it becomes impossible to appropriately control the torque of the engine.

An engine control device that solves the above problems calculates the engine torque from the throttle opening, which is the opening of the throttle valve installed in the intake passage of the engine mounted on the vehicle, and the engine operation amount other than the throttle opening. The engine torque is controlled by operating to achieve the target torque which is the control target value of the engine torque. The engine control device performs a maximum load factor calculation process that calculates the maximum load factor, which is the maximum value of the engine load factor at the current engine speed, and a process that sets the target torque according to the vehicle driving condition. There is a target torque setting process that sets a target torque value based on the maximum load factor so that the load factor is less than or equal to the maximum load factor, and a request for the load factor according to the target torque and engine rotation speed. A requested load factor calculation process that calculates the requested load factor, which is a value, a maximum opening load factor calculation process that calculates the maximum opening load factor based on the engine rotation speed, and a maximum opening load factor calculation process that calculates the maximum opening load factor based on the requested load factor and the maximum opening load factor. , is a process of calculating the target opening which is the control target value of the throttle opening, and when the requested load rate is equal to or higher than the maximum opening load rate, the maximum opening which is the maximum value of the control range of the throttle opening is calculated. It is calculated as the target opening value, and if the required load rate is less than the maximum opening load rate, the required load rate decreases from the maximum opening load rate. The target opening calculation process calculates the target opening as a value that decreases as the required load rate decreases from the maximum opening that is the value when the load rate is the same, and the throttle opening is adjusted so that the throttle opening becomes the target opening. Performs throttle operation processing to drive the valves.

The maximum load factor when the engine speed is constant is achieved when the throttle opening is at its maximum opening. Further, in the engine control device, the maximum opening is calculated as the value of the target opening when the required load factor is equal to or higher than the maximum opening load factor. Therefore, the maximum load factor and the maximum opening degree load factor are essentially the same value.

On the other hand, the control characteristics of the throttle valve can be adjusted by appropriately changing the value of the maximum opening degree load factor used to calculate the target opening degree. At this time, the engine control device separately calculates the maximum load factor used to set the target torque in torque control and the maximum opening load factor used to calculate the target opening in throttle opening control. Individual values are used. Therefore, it becomes possible to adjust the control characteristics of the throttle valve by changing the value of the maximum opening degree load factor without affecting the target torque setting in torque control. Therefore, according to the engine control device, a decrease in the degree of freedom in controlling the throttle opening degree for engine torque control can be suppressed.

The maximum load factor calculation process in the engine control device calculates the maximum load factor using a maximum load factor calculation map that is stored in advance in the control device and stores information about the relationship between the maximum load factor and the engine rotation speed. It is possible to perform a calculation process. Similarly, the maximum opening load factor is calculated using a maximum opening load factor calculation map that is stored in advance in the control device and stores information about the relationship between the maximum opening load factor and the engine speed. It is possible to perform the process of calculating the degree load factor. However, in such a case, as described below, there is a risk that the work of setting a calculation map when designing an engine control device may become complicated. For example, there may be a range of engine rotation speeds in which a common map value is set in both the maximum load factor calculation map and the maximum opening load factor calculation map. When the map values of the maximum load factor calculation map in such a common range are corrected, it is necessary to similarly correct the map values of the maximum opening load factor calculation map. On the other hand, when setting a calculation map, manual correction of map values may be repeated many times, and there is a risk that the map values of both calculation maps may become inconsistent due to forgotten correction or incorrect correction.

For this purpose, the engine control device has a maximum load factor calculation map that stores information about the relationship between the maximum load factor and the engine speed, and a load factor that is the difference between the maximum opening load factor and the maximum load factor. A correction value calculation map storing information about the relationship between correction values and engine speed is stored in advance. Then, the maximum load factor calculation process is the process of calculating the maximum load factor using the maximum load factor calculation map, and the maximum opening load factor calculation process is the maximum load calculated using the maximum load factor calculation map. It is preferable that the process calculates the maximum opening degree load factor by correcting the load factor with a load factor correction value calculated using a correction value calculation map. In such a case, in a part where "0" is set as the map value of the correction value calculation map, the maximum opening load factor will be the maximum load factor no matter how many times the map value of the maximum load factor calculation map for that part is corrected. The value will be the same. Therefore, when modifying the map value of the maximum load factor calculation map in the common portion, it is not necessary to modify the correction value calculation map. In this way, if the maximum opening degree load factor is calculated in the above manner, it becomes easy to set the calculation map when designing the engine control device.

By the way, in the large opening range near the maximum opening, the load factor changes only slightly in response to changes in the throttle opening, and so-called throttle hunting occurs, where large changes in the throttle opening are repeated in response to minute fluctuations in the required load factor. may occur. The occurrence of such throttle hunting in the large opening region can be suppressed by performing the target opening calculation processing in the engine control device in the following manner.

Here, the ratio of the intake pressure after passing through the throttle valve to the intake pressure before passing through the throttle valve is defined as the throttle front-rear pressure ratio RP, and the throttle opening when the throttle front-rear pressure ratio RP becomes the default value RPwot is the switching point. The opening degree is TAwot, the load rate KL when the throttle front-to-back pressure ratio RP becomes the default value RPwot is the switching point load rate KLwot, and the throttle front-to-back pressure ratio RP required to make the load rate the required load rate is the required pressure. Let the ratio be RP*. At this time, the target opening calculation processing in the engine control device is performed to target the throttle opening at which the throttle front and rear pressure ratio RP becomes the required pressure ratio RP* when the required pressure ratio RP* is less than the predetermined value RPwot. It is calculated as the opening value, and if the required pressure ratio RP* exceeds the default value RPwot, the switching point opening TAwot, the switching point load factor KLwot, the maximum opening TAmax, the maximum opening load factor KLmax2, The process calculates a value "TA*" that satisfies the relationship of equation (1) with respect to the required load factor KL* as the value of the target opening degree.

In the above target opening calculation process, when the required pressure ratio RP* is less than or equal to the predetermined value RPwot, the throttle opening TA at which the throttle front and rear pressure ratio RP becomes the required pressure ratio RP* is calculated as the value of the target opening TA*. be done. Even if the required pressure ratio RP* exceeds the default value RPwot, if the throttle opening TA at which the throttle front-rear pressure ratio RP becomes the required pressure ratio RP* is calculated as the value of the target opening TA*, the target opening TA* will be As the maximum opening degree TAmax approaches, the sensitivity of the target opening degree TA* to the load factor KL increases. Therefore, in the large opening range, the value of the target opening TA* changes greatly in response to a slight change in the required load factor KL*, resulting in throttle hunting.

On the other hand, in the target opening degree calculation process, if the required pressure ratio RP* exceeds the predetermined value RPwot, the value of the target opening degree TA* is calculated so that it has a linear relationship with the required load rate KL*. be done. In such a case, in a region where the required pressure ratio RP* exceeds the predetermined value RPwot, the rate of change of the target opening degree TA* with respect to the required load factor KL* is constant, so throttle hunting is less likely to occur.

Moreover, even in the large opening range, the target opening TA* is calculated as a value that changes in conjunction with the required load factor KL*, so gases other than fresh air, such as recirculated exhaust, fuel vapor, and blow-by gas, enter the combustion chamber. Even in a situation where the load factor KL* changes, it is possible to control the throttle opening degree TA so that the load factor KL changes in accordance with the change in the required load factor KL*. By performing the target opening calculation process in the above manner, controllability of the throttle valve in the large opening range can be improved.

1 is a diagram schematically showing the configuration of an embodiment of an engine control device. 2 is a flowchart of a torque control routine executed by the engine control device. A graph showing the relationship between the maximum load factor and engine speed stored in the maximum load factor calculation map. A graph showing the relationship between the throttle front and rear pressure ratio and the throttle passing flow rate. A graph showing the relationship between the throttle front and rear pressure ratio and the Φ value. A graph showing the relationship between saturated flow rate and throttle opening. Graph showing the relationship between throttle opening and throttle front-to-back pressure ratio. 5 is a flowchart of a throttle opening control routine executed by the engine control device. The graph which shows the relationship between the load factor correction value and engine rotation speed stored in the correction value calculation map. Graph showing the relationship between maximum load factor, maximum opening load factor, and engine speed. The figure which shows the calculation mode of the target opening degree in the large opening degree area. Graph showing the relationship between the required load factor and the target opening in the large opening range.

Hereinafter, one embodiment of the engine control device will be described in detail with reference to FIGS. 1 to 12. The engine control device of this embodiment is applied to a naturally aspirated engine mounted on a vehicle. The output of the engine is transmitted to the wheels as driving force for driving via the transmission.

As shown in FIG. 1, the engine 10 to which this embodiment is applied includes an intake passage 12 through which intake air flows into the combustion chamber 11, and an exhaust passage 13 through which exhaust gas discharged from the combustion chamber 11 flows. It is provided. The engine 10 also includes an intake valve 14 that communicates/cuts off the intake passage 12 with the combustion chamber 11 depending on whether the valve is opened/closed, and an exhaust passage 13 which communicates/cuts off the intake passage 12 with the combustion chamber 11 depending on whether the valve is opened or closed. A shutoff exhaust valve 15 is provided.

The intake passage 12 is provided with an air cleaner 16 that filters dust and the like in the intake air, and an air flow meter 17 that detects an intake flow rate GA that is the flow rate of intake air flowing through the intake passage 12. Further, a throttle valve 18 is installed in a portion of the intake passage 12 downstream of the air flow meter 17 . The throttle valve 18 is installed in the intake passage 12 in a rotatably supported state. The throttle valve 18 is rotationally driven by a throttle motor 19. Furthermore, an injector 20 that injects fuel into intake air is installed in a portion of the intake passage 12 downstream of the throttle valve 18. An ignition device 21 is installed in the combustion chamber 11 to ignite a mixture of intake air flowing through the intake passage 12 and fuel injected by the injector 20.

In such an engine 10, the throttle valve 18 is a valve that adjusts the throttle passage flow rate, which is the flow rate of intake air passing through the throttle valve 18, by changing the opening area according to the rotational position within the intake passage 12. There is. The throttle opening degree TA in the following description represents the rotation angle of the throttle valve 18 from the fully closed position, which is the rotational position where the opening area is "0".

The engine 10 configured as described above is controlled by an engine control system 22 serving as an engine control device. The engine control system 22 is configured as an electronic control unit that includes an arithmetic processing circuit that performs various arithmetic processing related to engine control, and a memory that stores programs and data. In addition to the intake flow rate GA detection signal from the air flow meter 17 described above, the engine control system 22 includes detection signals such as the accelerator pedal operation amount ACC, which is the amount of depression of the accelerator pedal by the driver, atmospheric pressure PA, throttle opening degree TA, etc. is entered. Furthermore, a pulsed crank signal CRNK that is output in accordance with the rotation of the crankshaft 23 is input to the engine control system 22 . The engine control system 22 determines the engine speed NE from the crank signal CRNK.

Note that in addition to the engine control system 22, various control systems are installed in the vehicle. For example, a shift control system that controls the speed change of a transmission, an auto-cruise control system that controls the vehicle's auto-cruise, a traction control system that performs traction control to prevent wheels from spinning, and a traction control system that controls the vehicle's attitude when turning. These include control systems such as a driving stability control system that performs driving stability control to stabilize the vehicle. In the following description, a control system other than the engine control system 22 installed in the vehicle will be referred to as another control system 30. The other control system 30 sets a required value of engine torque for each control and outputs it to the engine control system 22. In the following description, the engine torque request values set by each of the other control systems 30 will be referred to as other request torques TEr1, TEr2, . . . .

The engine control system 22 controls the torque of the engine 10 through a driver request torque calculation process F1, a maximum load factor calculation process F2, a target torque setting process F3, a throttle opening control process F4, and an ignition timing control process F5. ing. The driver requested torque calculation process F1 is a process that calculates the driver requested torque TEd, which is the driver's requested value of engine torque, based on the accelerator pedal operation amount ACC and the engine rotational speed NE. The maximum load factor calculation process F2 is a process to calculate the maximum load factor KLmax1 which is the maximum value of the load factor KL of the engine 10 at the current engine speed NE, and the target torque setting process F3 is a control target value of the engine torque. This is a process of setting target torque TE*. Further, the throttle opening control process F4 is a process for controlling the throttle opening TA of the throttle valve 18 according to the target torque TE*, and the ignition timing control process F5 is a process for controlling the ignition timing of the ignition device 21 according to the target torque TE*. This is a process for controlling SA.

Further, the engine control system 22 performs a throttle opening control process F4 through the required load factor calculation process F6, the maximum opening load rate calculation process F7, the target opening calculation process F8, and the throttle operation process F9. . The required load factor calculation process F6 is a process to calculate the required load rate KL*, which is the required value of the load rate KL, based on the target torque TE* and the engine speed NE, and the maximum opening load rate calculation process F7 is a process based on the engine rotation speed NE. This is a process of calculating the maximum opening load factor KLmax2 based on the number NE. The target opening calculation process F8 is a process for calculating a target opening TA*, which is a control target value of the throttle opening TA, based on the required load rate KL* and the maximum opening load rate KLmax2. The throttle operation process F9 is a process for driving the throttle valve 18 in order to set the throttle opening degree TA to the target opening degree TA*.

Next, details of such torque control of the engine 10 will be explained. FIG. 2 shows a flowchart of a torque control routine executed by engine control system 22 for torque control. While the engine 10 of the engine control system 22 is operating, the process of this routine is repeatedly executed at every predetermined control cycle.

When the processing of this routine is started, first in step S100, the driver required torque TEd is calculated based on the accelerator pedal operation amount ACC and the engine rotation speed NE. The driver requested torque TEd indicates the engine torque required to meet the driver's request for the driving force of the vehicle.

In the next step S110, other required torques TEr1, TEr2, . . . set by other control systems 30 are read. Then, in step S120, from among the driver requested torque TEd and other requested torques TEr1, TEr2, . . . , the requested torque that should be given the highest priority in the current vehicle driving situation is set as the value of the final requested torque TEr. .

In the subsequent step S130, the value of the maximum load factor KLmax1, which is the maximum value of the load factor KL of the engine 10 at the current engine speed NE, is calculated. The load factor KL is the mass of intake air flowing into the combustion chamber 11, which is the amount of intake air flowing into the cylinder, based on the standard atmospheric conditions that occupy the stroke volume of the cylinder, that is, standard atmospheric pressure: 1013 hPa, standard temperature: 20°C, and standard relative humidity: It is expressed as a ratio of 60% to the mass of intake air. That is, the load factor KL represents the filling efficiency ηc of intake air into the combustion chamber 11. The maximum load factor KLmax1 indicates the value of the load factor KL when the throttle opening TA is set to the maximum opening TAmax, which is the maximum value of the control range, at the current engine speed NE. This calculation of the maximum load factor KLmax1 is performed using a maximum load factor calculation map MAP1 stored in advance in the memory of the engine control system 22. The maximum load factor calculation map MAP1 stores information about the relationship between the engine speed NE and the maximum load factor KLmax1, which has been determined in advance through tests and the like. FIG. 3 shows the relationship between the engine speed NE and the maximum load factor KLmax1 in the maximum load factor calculation map MAP1 used in the engine control device of this embodiment.

Subsequently, in step S140, based on the maximum load factor KLmax1 and the engine speed NE, maximum torque TEmax, which is the engine torque when the load factor KL of the engine 10 is set to the maximum load factor KLmax1 at the current engine speed NE, is determined. The value is calculated. Then, in the subsequent step S150, the smaller value of the final required torque TEr and the maximum torque TEmax is set as the value of the target torque TE*.

In the next step S160, a throttle opening control process F4 is performed in which the throttle opening TA of the throttle valve 18 is manipulated according to the target torque TE*. Further, in the subsequent step S170, an ignition timing control process F5 is performed to manipulate the ignition timing SA of the ignition device 21 according to the target torque TE*.

In such a torque control routine, from among the driver requested torque TEd and other requested torques TEr1, TEr2, . . . , the requested torque that has the highest priority in the current vehicle driving situation is set as the value of the final requested torque TEr. On the other hand, the values of the other required torques TEr1, TEr2, ... are set depending on the circumstances of the other control systems 30, so they cannot be realized values that exceed the maximum torque TEmax of the engine 10 at the current engine speed NE. may be set. Therefore, in the above torque control routine, the maximum load rate KLmax1 at the current engine speed NE is determined, and the value of the target opening TA* is set so that the maximum torque TEmax obtained from the maximum load rate KLmax1 is equal to or less than the maximum torque TEmax. is set.

Note that there is a delay corresponding to the travel time of the intake air from the throttle valve 18 to the combustion chamber 11 before the change in the throttle opening TA is reflected in the engine torque. Therefore, the engine torque equivalent to the target torque TA* may not be achieved by controlling the throttle opening degree TA alone. Therefore, in this embodiment, in throttle opening control, the engine torque is brought closer to the target torque TE* as much as possible by operating the throttle opening TA, and the excess or deficiency caused by the delay due to the intake air travel time is adjusted to the ignition timing. By supplementing this by manipulating the ignition timing SA in the control, the engine torque equivalent to the target torque TE* is achieved.

In this torque control routine, the process of step S100 is the driver requested torque calculation process F1, the process of step S130 is the maximum load factor calculation process F2, and the process of steps S110, S120, S140, and S150 is the target torque. Each corresponds to the setting process F3.

Next, details of the throttle opening control process F4 in step S160 of the torque control routine will be explained. Here, first, the basic logic of calculating the target opening degree TA*, which is the control target value of the throttle opening degree TA, will be explained.

When calculating the target opening degree TA*, the engine control system 22 first calculates a required load factor KL*, which is a required value of the load factor KL, based on the target torque TE* and the engine speed NE. Here, a load factor KL that brings the engine torque to a value close to the target torque TE* within a realizable range taking into account the delay due to the intake air travel time is calculated as the value of the required load factor KL*.

On the other hand, the intake air amount flowing into the cylinder is determined by the throttle downstream pressure PM, which is the pressure of the intake air in the portion downstream of the throttle valve 18 in the intake passage 12, and the engine rotation speed NE. Therefore, based on the required load factor KL* and the engine speed NE, it is possible to determine the value of the throttle downstream pressure PM necessary to obtain the load factor KL corresponding to the required load factor KL*. The engine control system 22 calculates, as the value of the required throttle downstream pressure PM*, a throttle downstream pressure PM at which a load factor KL corresponding to the required load rate KL* is obtained based on the required load rate KL* and the engine speed NE. There is.

Here, the mass flow rate of intake air that passes through the throttle valve 18 and is distributed and supplied to the combustion chamber 11 of each cylinder of the engine 10 is defined as the intake valve passing flow rate. Note that the intake air flows into the combustion chamber 11 intermittently according to the opening and closing of the intake valve 14, so the actual intake valve passing flow rate is a value that fluctuates depending on the rotation of the engine 10. The value obtained by smoothing out the fluctuations is used as the intake valve passing flow rate. The number of intake strokes performed in the engine 10 during one rotation of the engine 10 is determined by the number of cylinders of the engine 10. Therefore, the engine rotation speed NE, which is the rotation speed of the engine 10 per unit time, is a value proportional to the number of intake strokes performed in the engine 10 per unit time, and the engine rotation speed NE is multiplied by the required load factor KL*. The product (=NE×KL*) is a value proportional to the intake valve passing flow rate at which the load factor KL corresponding to the required load factor KL* is obtained.

Note that in this embodiment, [rpm·%] is used as a unit of the intake air flow rate used to calculate the target opening degree TA*. When the same unit is used, the intake valve passing flow rate [rpm·%] becomes a value that matches the product of the engine rotation speed NE [rpm] multiplied by the required load factor KL*[%].

The intake valve passing flow rate in a steady state where the throttle opening degree TA and the engine speed NE are held constant is equal to the throttle passing flow rate, which is the flow rate of intake air passing through the throttle valve 18. Therefore, the throttle opening TA at which the throttle downstream pressure PM becomes the required throttle downstream pressure PM* and the throttle passing flow is the product of the engine speed NE and the required load factor KL* is set as the target opening TA* of the throttle valve 18. Then, a load factor KL equal to the required load factor KL* can be obtained.

The flow rate passing through the throttle is the product of the speed of intake air passing through the throttle valve 18 and the opening area of the throttle valve 18. Further, the opening area of the throttle valve 18 is a function of the throttle opening degree TA. Further, the speed of the intake air passing through the throttle valve 18 is determined by the throttle front-to-back pressure ratio RP, which is the ratio of the throttle downstream pressure PM to the throttle upstream pressure PAC. The throttle upstream pressure PAC represents the pressure of intake air in a portion of the intake passage 12 upstream of the throttle valve 18 . In this embodiment, atmospheric pressure PA is used as throttle upstream pressure PAC. The possible range of the value of the throttle front and rear pressure ratio RP is from "0" to "1". Therefore, if two values among the three values of throttle opening TA, throttle front-to-back pressure ratio RP, and throttle passage flow rate are determined, the remaining value will also be determined automatically.

FIG. 4 shows the relationship between the throttle opening TA, the throttle front and back pressure ratio RP, and the throttle passing flow rate. The speed of the intake air passing through the throttle valve 18 is "0" when the throttle front-to-back pressure ratio RP is "1", and becomes the sonic speed when the throttle front-to-back pressure ratio RP is below a certain value α. The speed of intake air passing through the throttle valve 18 when the throttle front-to-back pressure ratio RP is gradually increased from "α" to "1" is the value when the throttle front-to-back pressure ratio RP is "α". The speed of sound gradually decreases to "0", which is the value when the throttle front-to-back pressure ratio RP is "1". Further, the throttle passing flow rate is the product of the speed of intake air passing through the throttle valve 18 and the opening area of the throttle valve 18. Therefore, when the throttle front-back pressure ratio RP is constant, the larger the throttle opening TA, the larger the flow rate passing through the throttle. Therefore, the change tendency of the flow rate passing through the throttle with respect to the throttle opening degree TA and the throttle front-to-back pressure ratio RP is as shown in FIG.

Here, the flow rate passing through the throttle in a region where the throttle front-to-back pressure ratio RP is equal to or less than "α", that is, in a sonic speed region where the speed of intake air passing through the throttle valve 18 is equal to or higher than the speed of sound, is defined as the saturated flow rate. The saturated flow rate is the product of the opening area of the throttle valve 18 and the speed of sound, and its value is a function of the throttle opening TA. The ratio of the throttle passing flow rate to the saturation flow rate is defined as the Φ value. Since the speed of intake air passing through the throttle valve 18 is determined by the throttle front-to-back pressure ratio RP, the Φ value is a function of the throttle front-to-back pressure ratio RP. Note that the Φ value also represents the ratio of the speed of intake air passing through the throttle valve 18 to the speed of sound.

FIG. 5 shows the relationship between the Φ value and the throttle front and back pressure ratio RP. As shown in the figure, the Φ value is "1" in the sonic speed range where the throttle front-rear pressure ratio RP is "α" or less. Further, when the throttle front and rear pressure ratio RP is "1", the Φ value is "0". When the throttle front and rear pressure ratio RP is gradually increased from "α" to "1", the Φ value changes from "1", which is the value when the throttle front and rear pressure ratio RP is "α", to the throttle front and rear pressure ratio RP of "α". The value gradually decreases to "0", which is the value when the pressure ratio RP is "1". The memory of the engine control system 22 stores in advance a Φ value calculation map MAP2 that stores information about the relationship between the Φ value and the throttle longitudinal pressure ratio RP.

FIG. 6 shows the relationship between the saturated flow rate and the throttle opening TA. As described above, the saturated flow rate is proportional to the opening area of the throttle valve 18. Since the relationship between the throttle opening TA and the opening area is determined by the dimensions and shapes of the intake passage 12 and the throttle valve 18, the relationship between the saturated flow rate and the throttle opening TA is determined from their design specifications. There is. The memory of the engine control system 22 stores in advance an opening calculation map MAP3 in which information about the relationship between the saturated flow rate and the throttle opening TA is stored.

The throttle passing flow rate can be determined as the product of the saturated flow rate at the current throttle opening TA multiplied by the Φ value at the current throttle front-to-back pressure ratio RP. On the other hand, as described above, the required throttle downstream pressure PM* is determined as the value of the throttle downstream pressure PM that provides the load factor KL corresponding to the required load factor KL*. Therefore, if the current throttle upstream pressure PAC is known, the throttle front-to-back pressure ratio RP is such that the load factor KL for the required load factor KL* is obtained as the ratio of the required throttle downstream pressure PM* to the throttle upstream pressure PAC. The value of the required pressure ratio RP* can be determined. Incidentally, in the naturally aspirated engine 10, the throttle upstream pressure PAC can be considered to be the same pressure as the atmospheric pressure PA. Therefore, in this embodiment, the quotient (=PM*/PA) obtained by dividing the required throttle downstream pressure PM* by the atmospheric pressure PA is determined as the value of the required pressure ratio RP*.

Further, as described above, the intake valve passing flow rate at which the load factor KL corresponding to the required load factor KL* is obtained is the product of the required load factor KL* multiplied by the engine rotation speed NE. Further, in a steady state, the intake valve passing flow rate and the throttle passing flow rate are equal to each other. Therefore, the value of the target opening degree TA* required to obtain the load factor KL for the required load factor KL* can be calculated by the following procedure.

As described above, the required throttle downstream pressure PM* represents the throttle downstream pressure PM when the intake valve passing flow rate becomes a flow rate at which the load factor KL corresponding to the required load factor KL* is obtained. Therefore, the value of the required pressure ratio RP*, which is the ratio of the required throttle downstream pressure PM* to the throttle upstream pressure PAC, is the value when the intake valve passing flow becomes a flow rate at which the load factor KL for the required load factor KL* is obtained. It represents the throttle front and rear pressure ratio RP. Therefore, based on the relationship shown in Fig. 5, the value of Φ value when the throttle front-to-back pressure ratio RP is the required pressure ratio RP* is determined, and the load factor for the required load rate KL* is calculated based on the value of the determined Φ value. The quotient obtained by dividing the intake valve passing flow rate required to obtain KL is calculated. The value of this quotient represents the saturated flow rate at the throttle opening TA at which the load factor KL corresponding to the required load factor KL* is obtained, that is, at the target opening TA*. Therefore, based on the relationship shown in Fig. 6, if the throttle opening TA whose quotient value is the saturated flow rate is determined as the value of the target opening TA*, the throttle opening will yield the load factor KL for the required load factor KL*. TA can be calculated as the value of the target opening degree TA*.

However, when controlling the opening degree of the throttle valve 18 based on the target opening degree TA* calculated in this way, the following problem may occur.
FIG. 7 shows a change in the throttle front-rear pressure ratio RP when the throttle opening TA is changed while the throttle upstream pressure PAC and the engine speed NE are constant. When the throttle opening TA is increased from "0" to the maximum opening TAmax, the throttle front and rear pressure ratio RP changes from "0", which is the value when the throttle opening TA is "0", to the throttle opening TA increases to "1", which is the value when the maximum opening degree TAmax is reached. However, as the throttle opening TA approaches the maximum opening TAmax, the rate of change in the throttle front-to-back pressure ratio RP with respect to the throttle opening TA, that is, the ratio of the change in the throttle front-to-back pressure ratio RP to the change in the throttle opening TA gradually decreases. becomes smaller. Therefore, in a large opening region where the throttle front-to-back pressure ratio RP is close to "1", the sensitivity of the throttle front-to-back pressure ratio RP to the throttle opening TA becomes low. In other words, the value of the target opening degree TA* changes greatly in response to a slight change in the required load factor KL*. As a result, in the large opening range, so-called throttle hunting, in which the throttle opening TA is frequently changed significantly, may occur, and the load on the throttle motor 19 and the like may increase.

Furthermore, when accelerating the vehicle by depressing the accelerator pedal, the amount of intake air flowing into the cylinder is required to increase quickly. On the other hand, when calculating the target opening degree TA* using the above basic logic, if the accelerator pedal is not depressed until the required load rate KL* reaches the maximum load rate KLmax1, the maximum opening degree TAmax will be lower than the target opening degree TA*. Since it is not set as a value, the increase in the intake air amount flowing into the cylinder when the vehicle accelerates is slow.

Based on the above, in this embodiment, the throttle opening degree TA is controlled in the following manner.
FIG. 8 shows a flowchart of a throttle opening control routine that the engine control system 22 of this embodiment executes when controlling the throttle opening TA. The engine control system 22 controls the throttle opening TA in step S160 of the torque control routine through the processing of this routine.

When the processing of this routine is started, first in step S200, a value of the required load factor KL*, which is a required value of the load factor KL, is calculated based on the target torque TE* and the engine rotation speed NE. Subsequently, in step S210, a required throttle downstream pressure PM* is calculated from the required load factor KL* and the engine speed NE. Furthermore, in the next step S220, the quotient obtained by dividing the required throttle downstream pressure PM* by the throttle upstream pressure PAC is calculated as the value of the required pressure ratio RP*. As described above, in this embodiment applied to the naturally aspirated engine 10, the atmospheric pressure PA is used as the throttle upstream pressure PAC. Note that when applied to a supercharged engine, it is preferable to use the detected value or estimated value of the supercharging pressure as the value of the throttle upstream pressure PAC.

Subsequently, in step S230, it is determined whether the required pressure ratio RP* is a value larger than a predetermined value RPwot. The default value RPwot is set to a value smaller than the lower limit of the range of throttle front and rear pressures in which throttle hunting may occur (see FIG. 7). If the required pressure ratio RP* at this time is less than or equal to the predetermined value RPwot (S230: NO), the process proceeds to step S240. On the other hand, if the required pressure ratio RP* is larger than the predetermined value RPwot (S230: YES), the process proceeds to step S300.

When the required pressure ratio RP* is less than or equal to the predetermined value RPwot and the process proceeds to step S240, in step S240, using the above-mentioned Φ value calculation map MAP2, it is determined that the throttle front and rear pressure ratio RP is equal to the required pressure ratio RP*. The value of the Φ value at a certain time is determined as the value of the required Φ value PHY*. Furthermore, in step S240, the quotient obtained by dividing the product of the required load factor KL* and the engine speed NE by the required Φ value PHY* is calculated as the value of the required saturation flow rate BPM*. Subsequently, in step S250, the throttle opening TA at which the saturated flow rate becomes the required saturated flow rate BPM* is calculated as the value of the target opening TA* using the above-mentioned opening calculation map MAP3, and then the process proceeds to step S260. You can proceed. In this way, when the required pressure ratio RP* is less than or equal to the predetermined value RPwot, the target opening degree TA* is calculated according to the above-mentioned basic logic.

Then, when the process proceeds to step S260, in step S260, the drive control of the throttle valve 18 is performed so that the throttle opening TA becomes the target opening TA*, and then the process of this routine ends. be done. The drive control of the throttle valve 18 is performed, for example, by feedback-adjusting the drive current of the throttle motor 19 according to the deviation of the throttle opening TA from the target opening TA*.

On the other hand, if the required pressure ratio RP* is larger than the default value RPwot (S230: YES) and the process proceeds to step S300, the following two values are calculated in step S300. First, using the Φ value calculation map MAP2, the value of the Φ value when the throttle front-rear pressure ratio RP is a predetermined value RPwot is calculated as the value of the switching point Φ value PHYwot. Further, the quotient obtained by multiplying the required load factor KL* by the engine speed NE divided by the switching point Φ value PHYwot is calculated as the value of the switching point saturated flow rate BPMwot.

Subsequently, in step S310, the throttle opening TA at which the saturated flow rate becomes the switching point saturated flow rate BPMwot is calculated as the value of the switching point opening TAwot using the opening calculation map MAP3.

In the subsequent step S320, the value of the load factor KL at which the throttle front-to-back pressure ratio RP becomes the predetermined value RPwot is calculated as the value of the switching point load factor KLwot. When calculating the switching point load factor KLwot, first, the product of the throttle upstream pressure PAC multiplied by the predetermined value RPwot is determined as the value of the switching point throttle downstream pressure PMwot. On the other hand, the memory of the engine control system 22 stores in advance a load factor calculation map MAP4 that stores information about the relationship between the throttle downstream pressure PM, the engine speed NE, and the load factor KL. The value of the switching point load factor KLwot is calculated by using this load factor calculation map MAP4 to find the load factor KL at which the throttle downstream pressure PM becomes the switching point throttle downstream pressure PMwot at the current engine speed NE. There is. The value of the switching point load factor KLwot calculated in this way indicates the load factor KL when the throttle opening TA is set as the switching point opening TAwot without changing the control state of the engine 10 other than the throttle opening TA. ing.

Incidentally, in an engine equipped with a variable valve mechanism that varies the valve operating characteristics of the intake valve 14 such as valve timing and valve lift amount, the relationship between the throttle downstream pressure PM, the engine speed NE, and the load factor KL as described above is also changes in response to changes in the valve operating characteristics of the intake valve 14 by the variable valve mechanism. If such a change in the valve operating characteristics of the intake valve 14 by the variable valve mechanism has a large influence on the load rate KL, the throttle downstream pressure PM, the engine speed NE, the operation amount of the variable valve mechanism, and the load rate KL The load factor calculation map MAP4 is configured to store the relationship between. Then, using the load factor calculation map MAP4, it is preferable to calculate the switching point load factor KLwot from the current engine speed NE, the operation amount of the variable valve mechanism, and the switching point throttle downstream pressure PMwot.

Subsequently, in step S330, the value of the maximum load factor KLmax1, which is the maximum value of the load factor KL of the engine 10 at the current engine speed NE, calculated in step S130 of the torque control routine described above is read. Furthermore, in the next step S340, a load factor correction value CKM, which is the difference between the maximum load factor KLmax1 and the maximum opening degree load factor KLmax2, which will be described later, is determined based on the engine speed NE. The load factor correction value CKM is calculated using a correction value calculation map MAP5 stored in advance in the memory of the engine control system 22. The correction value calculation map MAP5 stores information regarding the relationship between the engine speed NE and the load factor correction value CKM.

FIG. 9 shows the relationship between the engine speed NE and the load factor correction value CKM in the correction value calculation map MAP5. As shown in the figure, positive values are in the range of engine speed NE less than "N1", and negative values are greater than "N2" in the range of engine speed NE from "N1" to "N2". In the range of the engine speed NE, "0" is set as the value of the load factor correction value CKM. In addition, in the range of the engine speed NE below "N1", the sensitivity of the throttle longitudinal pressure ratio RP to the throttle opening TA in the large opening range is particularly low, and this is the range of the engine speed NE where throttle hunting is likely to occur. ing. In addition, the range of engine speed NE from "N1" to "N2" is the range of engine speed NE where a rapid increase in the amount of intake air flowing into the cylinder during acceleration is particularly required in order to ensure the acceleration performance of the vehicle. It becomes.

Subsequently, in step S350, the sum of the maximum load factor KLmax1 and the load factor correction value CKM is determined as the value of the maximum opening degree load factor KLmax2. The maximum opening degree load factor KLmax2 indicates the minimum value in the range of values of the required load factor KL* where the target opening degree TA* is the maximum opening degree TAmax at the current engine speed NE.

FIG. 10 shows the relationship between the maximum load factor KLmax1, the maximum opening load factor KLmax2, and the engine speed NE. As described above, the maximum load factor KLmax1 is the maximum value of the load factor KL at the current engine speed NE, and is used to set the target torque TE* in torque control. On the other hand, as described above, the maximum opening degree load factor KLmax2 is the minimum value in the range of values of the required load factor KL* where the target opening degree TA* is the maximum opening degree TAmax. When the engine speed NE is constant, the load factor KL is maximum when the throttle opening TA is set to the maximum opening TAmax, so the maximum opening load factor KLmax2 should originally be the same value as the maximum load factor KLmax1. It is a parameter. However, in this embodiment, different values are set for the maximum load factor KLmax1 and the maximum opening load factor KLmax2 depending on the engine speed NE. The reason for this will be discussed later.

Then, in step S360, based on the switching point opening degree TAwot, the maximum opening degree TAmax, the required load factor KL*, the switching point load factor KLwot, and the maximum opening degree load factor KLmax2, a value that satisfies the relationship shown in equation (2) is set. The value of the target opening degree TA* is calculated. Then, in step S360, an upper limit guard process is performed on the target opening degree TA* so that the target opening degree TA* becomes a value equal to or less than the maximum opening degree TAmax, and then the process proceeds to step S260. In the upper limit guard process, if the target opening degree TA* is less than or equal to the maximum opening degree TAmax, the value of the target opening degree TA* is maintained as it is, and if the target opening degree TA* exceeds the maximum opening degree TAmax, the value of the target opening degree TA* is maintained at the maximum opening degree TAmax. The opening degree TAmax is reset as the value of the target opening degree TA*. Thereafter, in step S260, drive control of the throttle valve 18 is performed based on the target opening degree TA* set in step S360, and then the processing of this routine ends.

In this throttle opening control routine, the process of step S200 is the required load factor calculation process F6, the process of steps S320 to S340 is the maximum opening load rate calculation process F7, and the process of step S260 is the throttle operation process F9. , respectively. Further, the remaining processes in the throttle opening degree control routine, ie, the processes of steps S210 to 250, steps S300 to S320, and step S360, correspond to the target opening degree calculation process F8.

FIG. 11 shows a plot of each parameter of equation (2) on an orthogonal coordinate system with throttle opening degree TA and load factor KL as coordinate axes. The line segment LAB shown in the figure has a coordinate point A where the throttle opening TA is the switching point opening TAwot and the load factor KL is the switching point load factor KLwot, and the throttle opening TA is the maximum opening TAmax. , and the coordinate point B where the load factor KL is the maximum opening load factor KLmax2. In step S360, the value of the throttle opening TA at the coordinate point C where the load factor KL becomes the required load factor KL* on the line segment LAB or its extension is calculated as the value of the target opening TA*. That is, equation (2) is an equation for calculating the target opening degree TA* through linear interpolation between coordinate points A and B.

The operation and effects of this embodiment will be explained.
In the present embodiment, the driver request torque TEd based on the accelerator pedal operation amount ACC and other request torques TEr1, TEr2, etc. set by other control systems 30 are determined to be the most prioritized in the current vehicle driving situation. The required torque is selected and the value of the target torque TE* is set. Then, the throttle opening TA and ignition timing SA are controlled in order to achieve the engine torque corresponding to the target torque TE*. At that time, by calculating the maximum load factor KLmax1 of the engine 10 at the current engine speed NE, and performing an upper limit reduction guard on the target torque TE* so that the load factor KL becomes a value below the maximum load factor KLmax1, This prevents an unrealizable value from being set as the value of the target torque TE*.

On the other hand, when controlling the throttle opening TA, the throttle opening TA required to achieve the load factor KL for the required load factor KL* set according to the target torque TE* is set to the value of the target opening TA*. Calculate as When calculating the target opening degree TA*, the throttle front and rear pressure ratio RP that provides a load factor KL equal to the required load factor KL* is calculated as the value of the required pressure ratio RP*. When the required pressure ratio RP* is less than or equal to the predetermined value RPwot, the throttle opening TA at which the throttle longitudinal pressure ratio RP becomes the required pressure ratio RP* is determined based on the relationship between the throttle longitudinal pressure ratio RP and the throttle opening TA. is calculated as the value of the target opening degree TA*.

The curve L0 in FIG. 12 shows that even when the required pressure ratio RP* exceeds the predetermined value RPwot, the throttle front and rear pressure ratio RP is equal to or lower than the required pressure ratio RP, as in the case where the required pressure ratio RP* is less than or equal to the calculation switching pressure ratio RPwot. The relationship between the required load factor KL* and the target opening degree TA* is shown when the throttle opening degree TA of * is calculated as the value of the target opening degree TA*. In such a case, as the required load rate KL* approaches the maximum load rate KLmax1, the ratio of the amount of change in the target opening degree TA* to the amount of change in the required load rate KL*, that is, the target opening degree to the required load rate KL*. The sensitivity of TA* increases. Therefore, in the vicinity of the maximum opening TAmax, the value of the target opening TA* changes greatly in response to a slight change in the required load factor KL*, resulting in throttle hunting.

On the other hand, a curve L1 in FIG. 12 shows the required load rate KL* in the large opening area when the same value as the maximum load rate KLmax1 is set as the value of the maximum opening load rate KLmax2 in the engine control device of this embodiment. It shows the relationship with the target opening degree TA*. Further, a curve L2 in FIG. 12 shows the above relationship when a value K1 smaller than the maximum load factor KLmax1 is set as the value of the maximum opening load factor KLmax2 in the engine control device of this embodiment. Further, a curve L3 in FIG. 12 shows the above relationship when a value K2 larger than the maximum load factor KLmax1 is set as the value of the maximum opening load factor KLmax2 in the engine control device of this embodiment. In either case, in the large opening range from the switching point opening TAwot to the maximum opening TAmax, the rate of change of the target opening TA* with respect to the required load rate KL* is constant. Therefore, by appropriately setting values such as the default value RPwot, it is possible to suppress the occurrence of throttle hunting in the large opening range.

Note that, as in the case of curve L2 in FIG. 12, if a value K1 smaller than the maximum load factor KLmax1 is set as the value of the maximum opening load factor KLmax2, the required load factor smaller than the maximum load factor KLmax1. The target opening degree TA* is set to the maximum opening degree TAmax from KL*. Therefore, in order to accelerate the vehicle, when the accelerator pedal is depressed, the throttle opening TA is increased to the maximum opening more quickly than when the same value as the maximum load rate KLmax1 is set as the value of the maximum opening load rate KLmax2. TAmax will be reached. Therefore, in the present embodiment, the value of the maximum opening load factor KLmax2 is set to a value smaller than the maximum load factor KLmax1 in the range of the engine speed NE where a prompt increase in the amount of air flowing into the cylinder is required during acceleration. .

On the other hand, in the present embodiment, the sensitivity of the throttle longitudinal pressure ratio RP to the throttle opening TA in the large opening region is particularly low, and in the engine speed NE range where throttle hunting is likely to occur, the Thus, a value K2 larger than the maximum load rate KLmax1 is set as the value of the maximum opening degree load rate KLmax2. In such a case, if the ratio of the amount of change in the target opening degree TA* to the amount of change in the required load factor KL* in the range from the switching point load factor KLwot to the maximum load factor KLmax1 is the same value as the maximum load factor KLmax1, then the maximum opening load It is smaller than the case where it is set as the value of the rate KLmax2. Therefore, throttle hunting can be suppressed even in the range of the engine speed NE where the sensitivity of the throttle longitudinal pressure ratio RP to the throttle opening degree TA is particularly low.

In this embodiment, the control characteristics of the throttle valve 18 are adjusted by setting the maximum opening load factor KLmax2 to a value different from the actual maximum value of the load factor KL at the current engine speed NE. are doing. On the other hand, if a value larger than the actual maximum value of the load factor KL at the current engine speed NE is set as the value of the maximum load factor KLmax1, a torque larger than the achievable engine torque will become the target torque TE*. There is a possibility that it may be set as a value. In this way, the value of the maximum load factor KLmax1 used for setting the target torque TE* in the torque control of the engine 10 needs to be set to the actual maximum value of the load factor KL at the current engine speed NE. In this regard, in this embodiment, the maximum load factor KLmax1 is used in the torque control of the engine 10 as the value indicating the maximum value of the load factor KL at the current engine speed NE, while the maximum load factor KLmax1 is used in the control of the throttle opening degree TA. The degree load factor KLmax2 is used. That is, in this embodiment, in the torque control and the throttle opening degree TA control, separate values calculated separately are used as the maximum value of the load factor KL at the current engine speed NE. Therefore, the control characteristics of the throttle valve 18 can be adjusted without affecting torque control.

In this embodiment, the value of the maximum opening degree load factor KLmax2 is calculated by correcting the maximum load factor KLmax1 using the load factor correction value CKM calculated using the correction value calculation map MAP5. Of course, if you prepare a calculation map that stores information about the relationship between the engine speed NE and the maximum opening load factor KLmax2, you can calculate the maximum opening load factor KLmax2 from the engine speed NE without going through the above steps. The value of can be directly calculated. However, in such a case, as described below, there is a risk that the work of setting a calculation map when designing an engine control device may become complicated.

Here, a calculation map for directly calculating the maximum opening load factor KLmax2 from the engine speed NE as described above is referred to as a maximum opening load factor calculation map. As described above, in the present embodiment, in the range of the engine speed NE of "N2" or more, the value of the maximum opening degree load factor KLmax2 is set to the same value as the value of the maximum load factor KLmax1. In the following description, the range of the engine speed NE in which the same value as the maximum load factor KLmax1 is set as the value of the maximum opening load factor KLmax2 will be referred to as a common range. In the following description, the values of the maximum load factor KLmax1 and the maximum opening load factor KLmax2 for each engine speed NE in each calculation map will be referred to as map values.

When calculating the maximum opening load factor KLmax2 using the maximum opening load factor calculation map as described above, if the map value of the maximum load factor calculation map MAP1 in the above common range is modified when designing the engine control device, A similar correction of map values is required for the maximum opening load factor calculation map as well. The control system of the engine 10 is a complex system in which various elements are intertwined, and corrections may be repeated many times when setting a calculation map. Therefore, if the map value of the maximum opening load factor calculation map is corrected every time the map value of the maximum load factor calculation map MAP1 is corrected, there is a risk that the map values of both calculation maps will become inconsistent due to incorrect correction or forgetting to make corrections. There is.

On the other hand, in this embodiment, the maximum The opening load factor KLmax2 is calculated. In this case, for the part where "0" is set as the map value of the correction value calculation map MAP5, no matter how the map value of the maximum load factor calculation map MAP1 is modified, the same value as the maximum load factor KLmax1 is the maximum value. This will be calculated as the value of the opening load factor KLmax2. Therefore, when modifying the map values of the maximum load factor calculation map MAP1 in the common range, it is not necessary to modify the correction value calculation map MAP5. In addition, even in a range of engine speed NE other than the common range, even if only the map value of the maximum load factor calculation map MAP1 is corrected while maintaining the map value of the correction value calculation map MAP5, the maximum load factor KLmax1 and the maximum The relative relationship with the opening load factor KLmax2 is maintained. Therefore, even in ranges other than the common range, it may not be necessary to modify the correction value calculation map MAP5 in accordance with the modification of the map value of the maximum load factor calculation map MAP1. In this way, if the maximum opening degree load factor KLmax2 is calculated using the correction value calculation map MAP5, it becomes easy to set the calculation map when designing the engine control device.

According to the engine control device of the present embodiment described above, the following effects can be achieved.
(1) In this embodiment, for torque control and throttle opening TA control, separate values calculated separately are used as the maximum value of the load factor KL at the current engine speed NE, so the throttle valve The influence of adjustment of the control characteristics in No. 18 on torque control can be suppressed.

(2) In the present embodiment, the maximum opening load factor KLmax2 is calculated using the correction value calculation map MAP5 that stores information about the difference from the maximum load factor KLmax1. Therefore, the work of setting the calculation map at the time of design becomes easy.

(3) In the large opening region where the load factor KL exceeds the switching point load factor KLwot, the target opening is set as a value that satisfies a linear relationship with the required load factor KL* between the switching point opening TAwot and the maximum opening TAmax. The degree TA* is calculated. Therefore, throttle hunting is less likely to occur in the large opening range. Moreover, even in the large opening range, the target opening TA* is calculated as a value that changes in conjunction with the required load factor KL*, so gases other than fresh air, such as recirculated exhaust, fuel vapor, and blow-by gas, enter the combustion chamber. Even in a situation where the load factor KL* changes, it is possible to control the throttle opening degree TA so that the load factor KL changes in accordance with the change in the required load factor KL*. Therefore, the controllability of the throttle valve in the large opening range can be improved.

This embodiment can be modified and implemented as follows. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
- The calculation of the target opening TA* using the maximum opening load factor KLmax2 may be performed in a manner different from that of the above embodiment. For example, the ratio of the required load rate KL* to the maximum opening load rate KLmax2 may be determined, and the target opening TA* may be calculated using a calculation map that stores the relationship between that ratio and the target opening TA*. good.

- In the above embodiment, the maximum opening load factor KLmax2 is corrected by correcting the maximum load factor KLmax1 calculated using the maximum load factor calculation map MAP1 with the load factor correction value CKM calculated using the correction value calculation map MAP5. was calculating. A maximum opening load factor calculation map storing information about the relationship between the maximum opening load factor KLmax2 and the engine speed NE as described above is stored in advance in the engine control system 22, and the maximum opening load factor is calculated in advance. The maximum opening load factor KLmax2 may be directly calculated from the engine speed NE using a calculation map.

- In the above embodiment, the torque of the engine 10 is controlled through the operation of the throttle opening TA and the ignition timing SA. There are engine operation variables other than these that can be used to adjust the engine torque. For example, in an engine equipped with a variable valve mechanism that makes the valve operating characteristics of the intake valve 14 and the exhaust valve 15 variable, engine torque can be adjusted by manipulating the valve operating characteristics using the variable valve mechanism. Additionally, in engines equipped with variable capacity turbochargers, engine torque can be adjusted by controlling the capacity of the turbocharger. Even if the torque control is performed through the operation of the throttle opening TA and one or more engine operating quantities other than the throttle opening TA from among the engine operating quantities that can adjust the engine torque. good.

- In each of the above embodiments, a case has been described in which the throttle control device is applied to a naturally aspirated engine 10, but if supercharging pressure is used as the throttle upstream pressure PAC instead of atmospheric pressure PA, supercharging It can also be applied to engines.

10... Engine 11... Combustion chamber 12... Intake passage 13... Exhaust passage 14... Intake valve 15... Exhaust valve 16... Air cleaner 17... Air flow meter 18... Throttle valve 19... Throttle motor 20... Injector 21... Ignition device 22... Engine control system 23...Crankshaft 30...Other control systems

Claims (3)

The throttle opening, which is the opening of the throttle valve installed in the intake passage of the engine mounted on the vehicle, and the engine operation amount, which is different from the throttle opening, are defined as the engine torque, which is the control target value for the same engine torque. An engine control device that controls the torque of the engine by operating to achieve a target torque,
Maximum load factor calculation processing that calculates a maximum load factor that is the maximum value of the load factor of the engine at the current engine speed;
A process of setting the target torque according to a driving condition of the vehicle, the target torque being set based on the maximum load factor so that the load factor becomes a value equal to or less than the same maximum load factor. Torque setting processing,
a requested load factor calculation process that calculates a requested load factor that is a requested value of the load factor according to the target torque and the engine rotational speed;
Maximum opening load factor calculation processing that calculates a maximum opening load factor based on the engine speed;
A process of calculating a target opening, which is a control target value of the throttle opening, based on the requested load factor and the maximum opening load factor, where the requested load factor is greater than or equal to the maximum opening load factor. The maximum opening, which is the maximum value of the control range of the throttle opening, is calculated as the value of the target opening, and if the requested load rate is less than the maximum opening load rate, the requested load rate is decreases from the maximum opening load rate, the maximum opening, which is the value when the required load rate is the maximum opening load rate, decreases as the required load rate decreases. a target opening degree calculation process that calculates the target opening degree as a value;
a throttle operation process of driving the throttle valve so that the throttle opening becomes the target opening;
An engine control device that performs The engine control device includes a maximum load factor calculation map that stores information about the relationship between the maximum load factor and the engine speed, and a load factor correction that is the difference between the maximum opening load factor and the maximum load factor. A correction value calculation map storing information about the relationship between the value and the engine rotation speed is stored in advance,
The maximum load factor calculation process is a process of calculating the maximum load factor using the maximum load factor calculation map,
The maximum opening load factor calculation process is performed by correcting the maximum load factor calculated using the maximum load factor calculation map with the load factor correction value calculated using the correction value calculation map. The engine control device according to claim 1, wherein the processing is to calculate a maximum opening degree load factor. The ratio of the intake pressure after passing through the throttle valve to the intake pressure before passing through the throttle valve is defined as a throttle front-to-back pressure ratio RP, and the throttle opening when the throttle front-to-back pressure ratio RP becomes a predetermined value RPwot is a switching point. The opening degree is TAwot, the load rate KL when the throttle front-to-back pressure ratio RP becomes the predetermined value RPwot is the switching point load rate KLwot, and the throttle front-to-back pressure necessary to set the load rate to the required load rate. When the ratio RP is the required pressure ratio RP*,
In the target opening calculation process, when the required pressure ratio RP* becomes a value equal to or less than the predetermined value RPwot, the throttle opening at which the throttle longitudinal pressure ratio RP becomes the required pressure ratio RP* is set to the target opening. If the required pressure ratio RP* exceeds the predetermined value RPwot, the switching point opening TAwot, the switching point load factor KLwot, the maximum opening TAmax, the maximum opening The engine control device according to claim 1 or 2, wherein the process calculates a value "TA*" that satisfies the relationship of the following formula with respect to the load factor KLmax2 and the required load factor KL* as the value of the target opening degree.