JP2021156180A - Throttle control device - Google Patents

Abstract

To accurately limit output of an engine.SOLUTION: An engine control unit 30 sets a required load factor KL* as a value of a command load factor KLc when the required load factor KL* calculated from engine speed NE and accelerator pedal operation amount ACC reaches a value equal to or lower than a load factor limit value KLr calculated as a load factor at which shaft output of an engine reaches an output limit value, and sets the load factor limit value KLr as a value of the command load factor KLc when the required load factor KL* reaches a value exceeding the load factor limit value KLr. The engine control unit 30 calculates a throttle opening that can obtain a load factor corresponding to the value of the command load factor KLc as a value of a target opening TA*.SELECTED DRAWING: Figure 2

Description

The present invention relates to a throttle control device that controls the opening degree of the throttle valve of an engine.

In an in-vehicle engine or the like, the cylinder inflow intake amount, which is the amount of air flowing into the cylinder for each combustion, is adjusted by controlling the opening degree of the throttle valve. In the throttle valve opening control, the intake pressure after passing the throttle valve, that is, the required throttle downstream pressure PM *, which is the required value of the throttle downstream pressure, is obtained from the accelerator pedal operation amount, and the required throttle downstream pressure PM * is used. This is done by determining the target opening TA *.

In the large opening region where the throttle opening is large, the sensitivity of the flow rate of the intake air passing through the throttle valve to the throttle opening becomes low, so that the amount of change in the throttle opening required for changing the cylinder inflow intake amount increases. Therefore, in the large opening region, so-called throttle hunting, in which the throttle opening is frequently changed, is likely to occur.

On the other hand, conventionally, Patent Document 1 proposes a throttle control device that calculates a target opening degree TA * according to the equation (1) when the required throttle downstream pressure PM * is equal to or higher than the specified pressure P1. There is. “TAwot” in the equation (1) represents the throttle opening required to set the throttle downstream pressure to the pressure P1 specified above. Further, "ΔTC" in the equation (1) is a correction opening degree obtained by the equation (2). Note that "CD" in equation (2) is a coefficient determined according to the engine speed NE, and the ratio of the change in throttle downstream pressure to the change in throttle opening is the lower limit of the range in which throttle hunting can be suppressed. The value is set so as to be.

Japanese Unexamined Patent Publication No. 2006-118373

By the way, the shaft output of the engine may be limited to a range below a certain value due to circumstances such as legal regulations and tax classification. Consider limiting the shaft output by controlling the throttle opening. For example, regardless of the operating condition of the engine, if the upper limit value of the throttle opening range in which the shaft output is equal to or less than the limit value is obtained and the upper limit guard of the throttle opening is applied so as not to exceed the upper limit value, the shaft output can be increased. It can be limited to the limit value or less. However, since the relationship between the throttle opening and the cylinder inflow intake amount changes depending on the engine speed or the like, the throttle opening at which the shaft output reaches the limit value also changes depending on the engine speed or the like. Therefore, there is a possibility that the shaft output is unnecessarily limited only by the upper limit guard of the throttle opening.

The throttle control device that solves the above problems is a device that controls the throttle opening, which is the opening of the throttle valve installed in the intake passage of the engine, and is required by the engine based on the accelerator pedal operation amount and the engine rotation speed. The required load factor calculation process for calculating the load factor, and the load factor limit value calculation process for calculating the load factor of the engine whose shaft output of the engine is the default output limit value as the value of the load factor limit value based on the engine rotation speed. When the required load factor is less than or equal to the load factor limit value, the value of the required load factor is set as the value of the command load factor, and when the required load factor exceeds the load factor limit value, the value is set. The command load factor setting process that sets the value of the same load factor limit value as the value of the command load factor, and the target opening that calculates the throttle opening that obtains the load factor for the value of the command load factor as the value of the target opening. The calculation process and the throttle drive process for driving the throttle valve so as to set the throttle opening to the target opening are performed.

In the throttle control device, the target opening degree is calculated based on the command load factor set to be equal to or less than the load factor limit value. The value of the load factor limit value is calculated as a value indicating the load factor of the engine whose shaft output is the output limit value at the current engine speed. Therefore, until the opening at which the shaft output becomes the output limit value at the current engine speed, the opening at which the load factor corresponding to the value of the required load factor can be obtained is set as the target opening, and the shaft output becomes It becomes difficult to be restricted unnecessarily. Therefore, according to the throttle control device, the output of the engine can be accurately limited by controlling the throttle opening degree.

In the command load factor setting process in the throttle control device, the realized torque, which is the engine torque when the throttle opening is controlled so that the load factor corresponding to the value of the required load factor can be obtained, and the shaft output are set as the output limit values. In addition to calculating the torque limit value, which is the engine torque in the case, the case where the realized torque is less than or equal to the torque limit value is the case where the required load factor is less than or equal to the load factor limit value, while the realized torque is It is preferable to configure so that the case where the value exceeds the torque limit value is the case where the required load factor exceeds the load factor limit value. When calculating the realized torque and torque limit value in such a case, the engine output limit can be implemented more accurately by referring to the state quantity of the engine that affects the shaft output such as ignition timing and valve timing.

Here, the maximum value of the control range of the throttle opening is set to the maximum opening TAmax, the maximum value of the load factor in the current control state of the engine is set to the maximum load factor KLmax, and the throttle valve with respect to the intake pressure before passing through the throttle valve. The ratio of the intake pressure after passing is the throttle front-rear pressure ratio RP, the throttle front-rear pressure ratio RP required to make the load factor the command load factor KLc is the required pressure ratio RP *, and the throttle front-rear pressure ratio RP is the default value. The throttle opening when the RPwot is reached is the switching point opening TAwot, and the load factor when the throttle front-rear pressure ratio RP is the default value RPwot is the switching point load factor KLwot. At this time, the target opening degree calculation process in the throttle control device targets the throttle opening degree at which the throttle front-rear pressure ratio RP becomes the required pressure ratio RP * when the required pressure ratio RP * becomes a value equal to or less than the default value RPwot. In addition to calculating as the opening value, if the required pressure ratio RP * exceeds the default value RPwot, the value "TA *" that satisfies the relationship in equation (3) is calculated as the target opening value. It is good to do.

こうした場合の目標開度演算処理では、要求圧力比RP*が既定値RPwot以下の場合には、スロットル前後圧力比RPが要求圧力比RP*となるスロットル開度TAが目標開度TA*の値として演算される。要求圧力比RP*が既定値RPwotを超える場合にも、スロットル前後圧力比RPが要求圧力比RP*となるスロットル開度TAが目標開度TA*の値として演算すると、目標開度TA*が最大開度TAmaxに近づくにつれて、負荷率KLに対する目標開度TA*の感度が高くなる。そのため、大開度領域では、要求負荷率KL*の僅かな変化に対して目標開度TA*の値が大きく変化することになり、スロットルハンチングが発生してしまう。

In such a target opening calculation process, when the required pressure ratio RP * is equal to or less than the default value RPwot, the throttle opening TA is the value of the target opening TA *, where the throttle front-rear pressure ratio RP is the required pressure ratio RP *. Is calculated as. 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 calculated. As the maximum opening TAmax approaches, the sensitivity of the target opening TA * to the load factor KL increases. Therefore, in the large opening region, the value of the target opening TA * changes significantly with respect to a slight change in the required load factor KL *, and throttle hunting occurs.

On the other hand, in the above target opening calculation process, in the large opening region where the required pressure ratio RP * exceeds the default value RPwot, the value of the target opening TA * is linearly related to the required load factor KL *. It is calculated. In such a case, in the region where the required pressure ratio RP * exceeds the default value RPwot, the rate of change of the target opening TA * with respect to the required load factor KL * is constant, so that throttle hunting is less likely to occur.

Moreover, when the required load factor KL * is the maximum load factor KLmax, the target opening degree TA * is calculated so as to be the maximum opening degree TAmax, so that the engine torque can be increased to the maximum value that can be originally generated. In addition, since the target opening TA * is calculated as a value that changes in conjunction with the required load factor KL * even in the large opening region, gases other than fresh air such as recirculated exhaust, fuel vapor, and blow-by gas are emitted into the combustion chamber. It is possible to control the throttle opening TA so that the load factor KL changes according to the change in the required load factor KL * even in the situation where the gas flows into the gas. Therefore, the controllability of the throttle valve in the large opening region can be improved.

The schematic diagram of the structure of the throttle control device of 1st Embodiment. The control block diagram which shows the flow of the process which concerns on the throttle opening control executed by the throttle control device. A graph showing the relationship between the throttle front-rear pressure ratio, the throttle opening and the throttle passing flow rate. A graph showing the relationship between the throttle front-rear pressure ratio and the Φ value. The graph which shows the relationship between the throttle opening and the saturated flow rate. The flowchart of the output limitation routine executed by the throttle control device of 2nd Embodiment. The flowchart of the target opening calculation routine executed by the throttle control device. A graph showing the relationship between the throttle opening and the throttle front-rear pressure ratio. A graph showing the relationship between engine speed and maximum load factor. The figure which shows the calculation mode of the target opening degree in the large opening area in the target opening degree calculation routine.

Hereinafter, an embodiment of the throttle control device will be described in detail with reference to FIGS. 1 to 5. The engine control device of the present embodiment is applied to a naturally aspirated engine mounted on a vehicle.

As shown in FIG. 1, the engine 10 to which the present embodiment is applied includes an intake passage 12 through which the intake air flowing into the combustion chamber 11 flows and an exhaust passage 13 through which the exhaust gas discharged from the combustion chamber 11 flows. It is provided. Further, the engine 10 has an intake valve 14 that communicates / shuts off the intake passage 12 to the combustion chamber 11 according to valve opening / closing, and an exhaust passage 13 that communicates / shuts off the exhaust passage 13 to the combustion chamber 11 according to valve opening / closing. An exhaust valve 15 for shutting off is provided. Further, the engine 10 is provided with a valve timing variable mechanism 16 that changes the valve timing of the intake valve 14.

The intake passage 12 is provided with an air cleaner 17 for filtering dust and the like during intake, and an air flow meter 18 for detecting the flow rate of intake air (intake flow rate GA) flowing through the intake passage 12. Further, a throttle valve 19 is installed in a portion of the intake passage 12 on the downstream side of the air flow meter 18. The throttle valve 19 is installed in the intake passage 12 in a state in which the throttle valve 19 is rotatably supported by a shaft, and is rotationally driven by the throttle motor 20. Further, in a portion of the intake passage 12 on the downstream side of the throttle valve 19, an intake pressure sensor 21 that detects the throttle downstream pressure PM, which is the intake pressure of the portion, and an injector 22 that injects fuel during intake are provided. Is installed. An ignition device 23 is installed in the combustion chamber 11 to ignite a mixture of the intake air flowing in through the intake passage 12 and the fuel injected by the injector 22.

In such an engine 10, the throttle valve 19 serves as a valve for adjusting the flow rate of intake air passing through the throttle valve 19 (throttle passing flow rate) by changing the opening area according to the rotation position in the intake passage 12. There is. The throttle opening TA in the following description represents the rotation angle of the throttle valve 19 from the rotation position (fully closed position) where the opening area becomes 0.

The engine 10 configured as described above is controlled by the engine control unit 30. The engine control unit 30 includes an arithmetic processing unit 31 that executes various arithmetic processes related to engine control, and a storage device 32 that stores programs and data. The engine control unit 30 receives an intake flow rate GA detection signal from the above-mentioned air flow meter 18, a throttle downstream pressure PM detection signal from the intake pressure sensor 21, and an engine rotation speed NE detection signal from the crank angle sensor 25, respectively. It has been entered. Further, in the engine control unit 30, a detection signal of the accelerator pedal operation amount ACC, which is the amount of depression of the accelerator pedal 26 from the accelerator pedal sensor 27, and a detection signal of the atmospheric pressure PA from the atmospheric pressure sensor 28 are installed in the throttle motor 20. The detection signals of the throttle opening degree TA are input from the throttle sensor 29. The engine control unit 30 determines control command values such as throttle opening TA, fuel injection amount QI, ignition timing SA, and valve timing VT of the intake valve 14 based on these detection signals. Then, the engine control unit 30 controls the operating state of the engine 10 by operating the throttle motor 20, the injector 22, the ignition device 23, the valve timing variable mechanism 16, and the like based on the determined control command value.

By the way, in an in-vehicle engine, the shaft output of the engine may be limited so as not to exceed a predetermined output limit value due to circumstances such as legal regulations and tax classification. In this embodiment, the shaft output of the engine is limited by controlling the throttle opening TA.

FIG. 2 shows the processing flow of the engine control unit 30 related to the control of the throttle opening TA. The throttle opening TA is controlled through the required load factor calculation process F1, the load factor limit value calculation process F2, the command load factor setting process F3, the target opening degree calculation process F4, and the throttle drive process F5.

In the required load factor calculation process F1, the required load factor KL *, which is a required value of the load factor KL, is calculated based on the accelerator pedal operation amount ACC and the engine speed NE. The load factor KL is the standard atmospheric condition (standard atmospheric pressure: 1013 hPa, standard temperature: 20 ° C, standard relative humidity: 60%) that occupies the stroke volume of the cylinder with respect to the mass of intake air flowing into the combustion chamber 11 (the amount of air flowing into the cylinder). ) Is expressed as a ratio to the mass of the intake air. That is, the load factor KL represents the filling efficiency ηc of the intake air in the combustion chamber 11.

Further, in the load factor limit value calculation process F2, the load factor KL at which the shaft output of the engine 10 is the output limit value at the current engine speed NE is calculated as the value of the load factor limit value KLr based on the engine speed NE. NS. Then, in the command load factor setting process F3, the smaller value of the required load factor KL * and the load factor limit value KLr is set as the value of the command load factor KLc. That is, in the command load factor setting process F3, when the required load factor KL * is equal to or less than the load factor limit value KLr, the required load factor KL * is a value in which the required load factor KL * exceeds the load factor limit value KLr. If, the load factor limit value KLr is set as the value of the command load factor KLc, respectively.

Further, in the target opening degree calculation process F4, the throttle opening degree TA required to obtain the load factor KL corresponding to the command load factor KLc is calculated as the value of the target opening degree TA *. Then, in the throttle drive process F5, the drive control of the throttle valve 19 is performed so that the throttle opening degree TA is set to the target opening degree TA *. The drive control of the throttle valve 19 is performed, for example, by feedback-adjusting the drive current of the throttle motor 20 according to the deviation of the throttle opening TA with respect to the target opening TA *. In the present embodiment, the engine control unit 30 that controls the throttle opening degree TA corresponds to the throttle control device.

The shaft output of the engine 10 changes depending on the ignition timing SA, the valve timing VT of the intake valve 14, and the like, in addition to the engine speed NE and the load factor KL. Therefore, the output limit value used for the calculation of the load factor limit value KLr in the load factor limit value calculation process F2 is set to a value slightly smaller than the upper limit value of the shaft output that cannot be exceeded.

Subsequently, a detailed calculation mode of the target opening degree TA * in the target opening degree calculation processing F4 will be described.
The cylinder inflow intake amount of the engine 10 is a value determined by the intake pressure (hereinafter, referred to as throttle downstream pressure PM) of the portion downstream of the throttle valve 19 in the intake passage 12 and the engine rotation speed NE. Therefore, based on the command load factor KLc and the engine speed NE, the value of the throttle downstream pressure PM required to obtain the load factor KL corresponding to the command load factor KLc can be obtained. Therefore, the engine control unit 30 calculates the throttle downstream pressure PM at which the load factor KL for the command load factor KLc is obtained as the value of the required throttle downstream pressure PM * based on the command load factor KLc and the engine speed NE. There is.

Here, the mass flow rate of the intake air that passes through the throttle valve 19 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. Since the inflow of intake air into the combustion chamber 11 is performed intermittently according to the opening and closing of the intake valve 14, the actual flow rate passing through the intake valve becomes a value that fluctuates according to the rotation of the engine 10. The value obtained by averaging the fluctuations is used as the valve passing flow rate. The number of intake strokes performed in the engine 10 during one rotation of the engine 10 is a number determined by the number of cylinders of the engine 10. Therefore, the engine speed NE, which is the number of revolutions of the engine 10 per unit time, becomes a value proportional to the number of intake strokes performed in the unit time in the engine 10, and the engine speed NE is multiplied by the command load factor KLc. The product (= NE × KLc) is a value proportional to the flow rate through the intake valve from which the load factor KL corresponding to the command load factor KLc is obtained.

In this embodiment, [rpm ·%] is used as a unit of the flow rate of the intake air used for calculating the target opening degree TA *. When the same unit is used, the intake valve passing flow rate [rpm ·%] is a value that matches the product of the engine speed NE [rpm] multiplied by the command load factor KLc [%].

The flow rate through the intake valve in a steady state in which the throttle opening TA and the engine speed NE are kept constant is equal to the flow rate of the intake air passing through the throttle valve 19 (hereinafter referred to as the throttle passing flow rate). Therefore, the throttle opening TA, where the throttle downstream pressure PM is the required throttle downstream pressure PM * and the throttle passing flow rate is the product of the engine speed NE and the command load factor KLc, should be set as the target opening TA * of the throttle valve 19. For example, the load factor KL corresponding to the command load factor KLc can be obtained.

The throttle passing flow rate is the product of the speed of intake air passing through the throttle valve 19 and the opening area of the throttle valve 19. The opening area of the throttle valve 19 is a function of the throttle opening TA. Further, the speed of the intake air passing through the throttle valve 19 is the ratio of the throttle downstream pressure PM to the intake pressure (throttle upstream pressure PAC) of the portion upstream of the throttle valve 19 in the intake passage 12 (hereinafter, throttle front-rear pressure ratio RP). ). The range in which the value of the throttle front-rear pressure ratio RP can be taken is a range from 0 to 1. Therefore, if two of the three values of the throttle opening TA, the throttle front-rear pressure ratio RP, and the throttle passing flow rate are determined, the remaining one value is naturally determined.

FIG. 3 shows the relationship between the throttle opening TA, the throttle front-rear pressure ratio RP, and the throttle passing flow rate. The speed of intake air passing through the throttle valve 19 is "0" when the throttle front-rear pressure ratio RP is "1", and becomes a sound velocity when the throttle front-rear pressure ratio RP is a certain value α or less. The speed of intake air passing through the throttle valve 19 when the throttle front-rear pressure ratio RP is gradually increased from "α" to "1" is based on the sound velocity which is the value when the throttle front-rear pressure ratio RP is α. The throttle front-rear pressure ratio RP gradually decreases to "0", which is the value when "1". Further, the throttle passing flow rate is the product of the speed of the intake air passing through the throttle valve 19 and the opening area of the throttle valve 19. Therefore, when the throttle front-rear pressure ratio RP is constant, the larger the throttle opening TA, the larger the throttle passing flow rate. Therefore, the tendency of the throttle passing flow rate to change with respect to the throttle opening TA and the throttle front-rear pressure ratio RP is as shown in FIG.

Here, the throttle passing flow rate in the region (sound velocity range) where the throttle front-rear pressure ratio RP is α or less is defined as the saturation flow rate. The saturated flow rate is the product of the opening area of the throttle valve 19 and the speed of sound, and the value is a function of the throttle opening TA. The ratio of the throttle passing flow rate to the saturated flow rate is defined as the Φ value. Since the speed of intake air passing through the throttle valve 19 is determined by the throttle front-rear pressure ratio RP, the Φ value is a function of the throttle front-rear pressure ratio RP. The Φ value also represents the ratio of the speed of the intake air passing through the throttle valve 19 to the speed of sound.

FIG. 4 shows the relationship between the Φ value and the throttle front-rear pressure ratio RP. As shown in the figure, the Φ value in the sound velocity range where the throttle front-rear pressure ratio RP is α or less is “1”. Further, when the throttle front-rear pressure ratio RP is "1", the Φ value is "0". The Φ value when the throttle front-rear pressure ratio RP is gradually increased from "α" to "1" is the value when the throttle front-rear pressure ratio RP is "α" from "1" before and after the throttle. The value gradually decreases to "0", which is the value when the pressure ratio RP is "1". In the storage device 32 of the engine control unit 30, the relationship between the Φ value and the throttle front-rear pressure ratio RP is stored as the Φ value calculation map MAP1.

FIG. 5 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 19. Since the relationship between the throttle opening TA and the opening area is determined by the dimensions and shape of the intake passage 12 and the throttle valve 19, the relationship between the saturated flow rate and the throttle opening TA is obtained from their design specifications. There is. The storage device 32 of the engine control unit 30 stores the relationship between the saturation flow rate and the throttle opening degree TA as the opening degree calculation map MAP2.

The throttle passing flow rate can be obtained as the product of the saturated flow rate at the current throttle opening TA and the Φ value at the current throttle front-rear pressure ratio RP. On the other hand, as described above, the required throttle downstream pressure PM * is obtained as the value of the throttle downstream pressure PM from which the load factor KL corresponding to the command load factor KLc can be obtained. Therefore, if the current throttle upstream pressure PAC is known, the throttle front-rear pressure ratio RP (hereinafter, hereafter, the load factor KL corresponding to the command load factor KLc can be 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 *) is obtained. By the way, in the naturally aspirated engine 10, the throttle upstream pressure PAC can be regarded as the same pressure as the atmospheric pressure PA. Therefore, in the present embodiment, the quotient (= PM * / PA) obtained by dividing the required throttle downstream pressure PM * by the atmospheric pressure PA is obtained 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 command load factor KLc is obtained is the product of the command load factor KLc multiplied by the engine speed NE. Further, in the steady state, the flow rate passing through the intake valve and the flow rate passing through the throttle are equal to each other. Therefore, the value of the target opening TA * required to obtain the load factor KL corresponding to the command load factor KLc can be calculated by the following procedure.

As described above, the required throttle downstream pressure PM * represents the throttle downstream pressure PM when the flow rate passing through the intake valve becomes the flow rate at which the load factor KL corresponding to the command load factor KLc can be 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 (atmospheric pressure PA is used in this embodiment), is a load in which the intake valve passing flow rate is the command load factor KLc. It represents the throttle front-rear pressure ratio RP when the flow rate at which the rate KL can be obtained. Therefore, based on the relationship shown in FIG. 3, the value of the Φ value when the throttle front-rear pressure ratio RP is the required pressure ratio RP * is obtained, and the load factor KL corresponding to the command load factor KLc is obtained from the obtained Φ value value. Calculate the quotient by dividing the intake valve passing flow rate required to obtain. The value of this quotient represents the saturated flow rate at the throttle opening TA, that is, the target opening TA *, at which the load factor KL corresponding to the command load factor KLc is obtained. Therefore, based on the relationship shown in FIG. 5, if the throttle opening TA at which the quotient value is the saturated flow rate is obtained as the value of the target opening TA *, the throttle opening TA can obtain the load factor KL corresponding to the command load factor KLc. Can be calculated as the value of the target opening TA *.

The operation and effect of this embodiment will be described.
In the throttle control device of the present embodiment, in the required load factor calculation process F1, the load factor KL of the engine 10 in response to the driver's acceleration / deceleration request is set as the value of the required load factor KL * based on the accelerator pedal operation amount ACC and the like. It is calculated. Further, in the load factor limit value calculation process F2, the load factor KL at which the shaft output of the engine 10 is the output limit value is calculated as the value of the load factor limit value KLr. Then, in the command load factor setting process F3, the smaller of the two values of the required load factor KL * and the load factor limit value KLr is set as the value of the command load factor KLc. Further, in the target opening degree calculation process F4, the throttle front-rear pressure ratio RP at which the flow rate passing through the intake valve is the flow rate at which the load factor KL corresponding to the command load factor KLc is obtained is calculated as the value of the required pressure ratio RP *. .. Then, the throttle opening TA required to make the throttle front-rear pressure ratio RP the required pressure ratio RP * is calculated as the value of the target opening TA *. Therefore, in the range where the shaft output is equal to or less than the output limit value, the throttle opening TA at which the load factor KL corresponding to the value of the required load factor KL * is obtained is set as the target opening TA *, and the engine 10 Shaft output is rarely unnecessarily limited. Therefore, the output limitation of the engine 10 can be accurately implemented by controlling the throttle opening degree TA.

(Second Embodiment)
Subsequently, a second embodiment of the throttle control device will be described in detail with reference to FIGS. 6 to 10. In the present embodiment, the same reference numerals are given to the configurations common to the above-described embodiments, and detailed description thereof will be omitted.

FIG. 6 shows a flowchart of an output limiting routine executed by the throttle control device of the present embodiment to set the command load factor KLc. The engine control unit 30 in the present embodiment repeatedly executes the processing of this routine every predetermined control cycle during the operation of the engine 10. In the present embodiment, the processing corresponding to each of the required load factor calculation process, the load factor limit value calculation process, and the command load factor setting process is performed in this routine.

When the processing of this routine is started, first, in step S100, the engine 10 such as engine speed NE, accelerator pedal operation amount ACC, ignition timing SA, valve timing VT of intake valve 14, throttle downstream pressure PM, atmospheric pressure PA, etc. The state quantity of is read. Then, in the following step S110, the required load factor KL * is calculated based on the engine speed NE and the accelerator pedal operation amount ACC.

In the next step S120, the value of the realized torque TR * is calculated based on the required load factor KL *, the engine speed NE, the ignition timing SA, and the valve timing VT of the intake valve 14. The realized torque TR * indicates the engine torque when only the load factor KL of the engine 10 is changed to the required load factor KL * under the current engine speed NE, ignition timing SA, and valve timing VT. Further, in the following step S130, the value of the torque limit value TRr is calculated based on the engine speed NE. The torque limit value TRr indicates the engine torque required to set the shaft output of the engine 10 as the output limit value at the current engine speed NE.

Then, in the next step S140, it is determined whether or not the realized torque TR * exceeds the torque limit value TRr. When the realized torque TR * is equal to or less than the torque limit value TRr (NO), in step S150, the value of the required load factor KL * is set as it is as the value of the command load factor KLc, and then the processing of this routine is performed. It will be terminated.

On the other hand, when the realized torque TR * exceeds the torque limit value TRr (YES), the process proceeds to step S160, and in that step S160, the load at which the shaft output of the engine 10 becomes the output limit value. The rate KL is calculated as the value of the load factor limit value KLr. Then, in the subsequent step S170, after the value of the load factor limit value KLr is calculated as the value of the command load factor KLc, the processing of this routine is terminated.

FIG. 7 shows a flowchart of a target opening calculation routine executed by the throttle control device of the present embodiment to calculate the target opening TA *. The engine control unit 30 executes the processing of this routine following the processing of the command load factor setting routine.

When the processing of this routine is started, first, in step S200, the detected values of the accelerator pedal operation amount ACC, the engine speed NE, and the atmospheric pressure PA, and the value of the command load factor KLc set in the above-mentioned output limiting routine are changed. To be acquired. Subsequently, in step S210, the required throttle downstream pressure PM * is calculated based on the engine speed NE and the command load factor KLc. Further in step S220, the quotient obtained by dividing the required throttle downstream pressure PM * by the throttle upstream pressure PAC (atmospheric pressure PA is used in this embodiment) is calculated as the value of the required pressure ratio RP *. When applied to a supercharged engine, the detected value or estimated value of the supercharging pressure may be used as the value of the throttle upstream pressure PAC.

Subsequently, in step S230, it is determined whether or not the required pressure ratio RP * is a value larger than the default value RPwot. If the required pressure ratio RP * at this time is a value equal to or less than the default value RPwot (S230: NO), the process proceeds to step S250. On the other hand, when the required pressure ratio RP * is a value larger than the default value RPwot (YES), the process proceeds to step S270.

As shown in FIG. 8, when the throttle opening TA approaches the maximum opening TAmax, the rate of change of the throttle front-rear pressure ratio RP with respect to the throttle opening TA (the amount of change of the throttle front-rear pressure ratio RP with respect to the change amount of the throttle opening TA). Ratio) gradually decreases. Therefore, in the large opening region where the throttle front-rear pressure ratio RP is close to 1, the sensitivity of the throttle front-rear pressure ratio RP to the throttle opening TA becomes low. That is, the value of the target opening degree TA * changes significantly with respect to a slight change in the required load factor KL *. As a result, in the large opening region, the throttle opening TA is frequently changed, that is, so-called throttle hunting occurs, which may impose a large load on the throttle motor 20 and the like. The default value RPwot is set to a value smaller than the lower limit of the throttle front-rear pressure range in which throttle hunting may occur.

Now, when the required pressure ratio RP * is a value equal to or less than the default value RPwot and the processing proceeds to step S250, in that step S250, the throttle front-rear pressure ratio RP is the required pressure using the above-mentioned Φ value calculation map MAP1. The value of the Φ value when the ratio is RP * is obtained as the value of the required Φ value PHY *. Then, in step S250, 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 saturated flow rate BPM *. Subsequently, in step S260, 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 opening calculation map MAP2, and then the processing of this routine is performed. It will be terminated.

On the other hand, when the required pressure ratio RP * is larger than the default value RPwot and the processing is advanced to step S270, the following two values are calculated in step S270. First, using the Φ value calculation map MAP1, the value of the Φ value when the throttle front-rear pressure ratio RP is the default value RPwot is calculated as the value of the switching point Φ value PHYwot. Further, the quotient obtained by dividing the product obtained by multiplying the command load factor KLc by the engine speed NE by the switching point Φ value PHYwot is calculated as the value of the switching point saturation flow rate BPMwot.

Subsequently, in step S280, the throttle opening TA at which the saturation flow rate becomes the switching point saturation flow rate BPMwot is calculated as the value of the switching point opening TAwot using the opening calculation map MAP2.
Further in step S290, the value of the load factor KL at which the throttle front-rear pressure ratio RP is the default 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 (atmospheric pressure PA is used in this embodiment) multiplied by the default value RPwot is obtained as the value of the switching point throttle downstream pressure PMwot. On the other hand, in the memory of the engine control unit 30, the relationship between the throttle downstream pressure PM, the engine speed NE, and the load factor KL is stored as the load factor calculation map MAP3. The value of the switching point load factor KLwot is calculated by using this load factor calculation map MAP3 to obtain 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 to the switching point opening TAwot without changing the control state of the engine 10 other than the throttle opening TA. ing.

By the way, in the engine 10 in which the valve timing variable mechanism 16 for changing the valve timing VT of the intake valve 14 is installed, the load factor KL changes depending on the valve timing VT in addition to the throttle downstream pressure PM and the engine rotation speed NE. .. When the change in the load factor KL due to the valve timing VT is large, the load factor calculation map MAP3 is configured to store the throttle downstream pressure PM, the engine speed NE, and the relationship between the valve timing VT and the load factor KL. .. Then, using the load factor calculation map MAP3, the switching point load factor KLwot may be calculated from the current engine speed NE, valve timing VT, and switching point throttle downstream pressure PMwot.

Subsequently, in step S300, the maximum load factor KLmax, which is the maximum value of the load factor KL at the current engine speed NE, is calculated. The calculation of the maximum load factor KLmax here is performed using the maximum load factor calculation map MAP4 in which the relationship between the engine speed NE and the maximum load factor KLmax in the engine 10 as shown in FIG. 9 is stored. The value of the maximum load factor KLmax calculated in this way is the load factor when the throttle opening TA is set to the maximum opening TAmax without changing the control state other than the throttle opening TA in the current operating state of the engine 10. Shows KL.

Further, in the following step S310, a value satisfying the relationship of the equation (4) is calculated as a value of the target opening degree TA *. Then, after the calculation, the processing of this routine is completed.

図１０に、スロットル開度TA及び負荷率KLを座標軸とした直交座標系に式（４）の各パラメータをプロットしたものを示す。同図に示す線分ＬＡＢは、スロットル開度TAが切替点開度TAwotであり、且つ負荷率KLが切替点負荷率KLwotである座標点Ａと、スロットル開度TAが最大開度TAmaxであり、且つ負荷率KLが最大負荷率KLmaxである座標点Ｂと、を繋ぐ線分である。ステップＳ３１０では、線分ＬＡＢ上において、負荷率KLが指令負荷率KLcとなる座標点Ｃのスロットル開度TAの値が、目標開度TA*の値として演算される。すなわち、式（４）は、座標点Ａ、Ｂ間の線形補間を通じて目標開度TA*を演算する式となっている。

FIG. 10 shows a plot of each parameter of Eq. (4) on a Cartesian coordinate system with the throttle opening TA and the load factor KL as coordinate axes. The line segment LAB shown in the figure has a coordinate point A in which 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, it is a line segment connecting the coordinate point B in which the load factor KL is the maximum load factor KLmax. In step S310, the value of the throttle opening TA at the coordinate point C where the load factor KL is the command load factor KLc on the line segment LAB is calculated as the value of the target opening TA *. That is, the equation (4) is an equation for calculating the target opening degree TA * through linear interpolation between the coordinate points A and B.

The operation and effect of this embodiment will be described.
In the target opening calculation process F4 in the throttle control device of the present embodiment, the throttle opening required to realize the load factor KL of the required load factor KL * obtained from the accelerator pedal operation amount ACC and the engine rotation speed NE. This is done to calculate the degree TA as the value of the target opening TA *. Then, when calculating the target opening degree TA *, the throttle front-rear pressure ratio RP at which the load factor KL corresponding to the command load factor KLc is obtained is calculated as the value of the required pressure ratio RP *. When the required pressure ratio RP * is equal to or less than the default value RPwot, the throttle opening TA where the throttle front-rear pressure ratio RP becomes the required pressure ratio RP * based on the relationship between the throttle front-rear pressure ratio RP and the throttle opening TA. Is calculated as the value of the target opening TA *.

In FIG. 10, even when the required pressure ratio RP * exceeds the default value RPwot, the throttle where the throttle front-rear pressure ratio RP becomes the required pressure ratio RP *, as in the case where the required pressure ratio RP * is equal to or less than the default value RPwot. The relationship between the command load factor KLc and the target opening TA * when the opening TA is calculated as the value of the target opening TA * is shown by the alternate long and short dash line. As shown in the figure, in such a case, as the target opening TA * approaches the maximum opening TAmax, the sensitivity of the target opening TA * to the load factor KL increases. Therefore, in the large opening region, the value of the target opening TA * changes significantly with respect to a slight change in the command load factor KLc, and throttle hunting occurs.

On the other hand, in the present embodiment, when the required pressure ratio RP * exceeds the default value RPwot, the target opening degree TA * is calculated in the following embodiment. That is, when calculating the target opening TA * in this case, the switching point opening TAwot, which is the throttle opening TA in which the throttle front-rear pressure ratio RP is the default value RPwot, is obtained. Further, the load factor KL when the throttle opening TA is the switching point opening TAwot is the value of the switching point load factor KLwot, and the load factor KL when the throttle opening TA is the maximum opening TAmax is the maximum load factor KLmax. It is calculated as the value of. In such a case, in the large opening region where the throttle opening TA is equal to or greater than the switching point opening TAwot, the target opening TA * is calculated as a value having a linear relationship with the command load factor KLc. As a result, the rate of change of the target opening TA * with respect to the command load factor KLc in the large opening region becomes constant, so that throttle hunting is less likely to occur.

Further, since the target opening TA * when the command load factor KLc becomes the maximum load factor KLmax becomes the maximum opening TAmax, the engine torque can be increased to the maximum value that can be originally generated. Further, the target opening TA * is calculated as a value that changes in conjunction with the command load factor KLc even in the large opening region. Therefore, even in a situation where gas other than fresh air such as recirculated exhaust, fuel vapor, and blow-by gas flows into the combustion chamber 11, the throttle opening TA is such that the load factor KL changes according to the change in the command load factor KLc. Can be controlled.

Further, also in the present embodiment, the output of the engine 10 is limited so that the shaft output becomes equal to or less than the output limit value through the control of the throttle opening TA. In the present embodiment, the engine when the load factor KL is set to the required load factor KL * based on the required load factor KL *, the engine speed NE, the ignition timing SA, and the valve timing VT of the intake valve 14 at the time of such output limitation. The realized torque TR *, which is the torque, is calculated. Further, the torque limit value TRr, which is the engine torque when the shaft output of the engine 10 is set as the output limit value, is calculated based on the engine speed NE, the ignition timing SA, and the valve timing VT of the intake valve 14. Then, when the realized torque TR * exceeds the torque limit value TRr, the load factor limit value KLr, which is the load factor KL at which the shaft output becomes the output limit value, is set as the value of the command load factor KLc, and the target opening TA * Is calculated to limit the output of the engine 10. As a result, the target opening degree TA * for reducing the shaft output of the engine 10 to the output limit value or less is calculated by reflecting the change in the shaft output due to the ignition timing SA and the valve timing VT. Therefore, the throttle control device of the present embodiment can limit the output of the engine 10 more accurately than the case of the first embodiment.

This embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
-In the calculation of the realized torque TR * and the torque limit value TRr in the second embodiment, in addition to the ignition timing SA and the valve timing VT, other state quantities that affect the shaft output may be referred to. For example, in an engine provided with an exhaust gas recirculation system in which a part of the exhaust is recirculated during intake, the amount of exhaust gas recirculation by the system is a state amount that affects the shaft output.

-The command load factor KLc in the first embodiment may be set in the mode of the second embodiment. Further, the calculation of the target opening degree TA * based on the command load factor KLc in the second embodiment may be performed in the embodiment of the first embodiment.

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

10 ... Engine 11 ... Combustion chamber 12 ... Intake passage 13 ... Exhaust passage 14 ... Intake valve 15 ... Exhaust valve 16 ... Valve timing variable mechanism 17 ... Air cleaner 18 ... Air flow meter 19 ... Throttle valve 20 ... Throttle motor 21 ... Intake pressure sensor 22 ... Injector 23 ... Ignition plug 24 ... Crankshaft 25 ... Crank angle sensor 26 ... Accelerator pedal 27 ... Accelerator pedal sensor 28 ... Atmospheric pressure sensor 29 ... Throttle sensor 30 ... Engine control unit 31 ... Arithmetic processing device 32 ... Storage device

Claims (3)

A throttle control device that controls the throttle opening, which is the opening of the throttle valve installed in the intake passage of the engine.
The required load factor calculation process that calculates the required load factor of the engine based on the accelerator pedal operation amount and the engine speed, and
Based on the engine speed, the load factor limit value calculation process for calculating the load factor of the engine whose shaft output of the engine is the default output limit value as the value of the load factor limit value, and
When the required load factor is equal to or less than the load factor limit value, the value of the required load factor is set as the value of the command load factor, and the required load factor becomes a value exceeding the load factor limit value. In this case, the command load factor setting process for setting the value of the same load factor limit value as the value of the command load factor, and the command load factor setting process.
Target opening calculation processing that calculates the throttle opening that obtains the load factor corresponding to the value of the command load factor as the value of the target opening, and
Throttle drive processing that drives the throttle valve to set the throttle opening to the target opening,
Throttle controller to do. In the command load factor setting process, the realized torque, which is the engine torque when the throttle opening is controlled so that the load factor corresponding to the value of the required load factor can be obtained, and the shaft output are set to the output limit value. The torque limit value, which is the engine torque in the case, is calculated, and the case where the realized torque is equal to or less than the torque limit value is defined as the case where the required load factor is equal to or less than the load factor limit value. The throttle control device according to claim 1, wherein the case where the realized torque exceeds the torque limit value is the case where the required load factor exceeds the load factor limit value. The maximum value of the control range of the throttle opening is set to the maximum opening TAmax, the maximum value of the load factor in the current control state of the engine is set to the maximum load factor KLmax, and the throttle valve of the same throttle valve with respect to the intake pressure before passing through the throttle valve. The ratio of the intake pressure after passing is the throttle front-rear pressure ratio RP, the throttle front-rear pressure ratio RP required to make the load factor the command load factor KLc is the required pressure ratio RP *, and the throttle front-rear pressure ratio RP is the default. When the throttle opening when the value is RPwot is the switching point opening TAwot and the load factor when the throttle front-rear pressure ratio RP is the default value RPwot is the switching point load factor KLwot.
The target opening degree calculation process sets the throttle opening degree at which the throttle front-rear pressure ratio RP becomes the required pressure ratio RP * when the required pressure ratio RP * becomes a value equal to or less than the default value RPwot. In addition to calculating as the value of, when the required pressure ratio RP * exceeds the default value RPwot, the value "TA *" satisfying the relationship of the following equation is calculated as the value of the target opening degree. The throttle control device according to claim 1 or 2.

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